Population Studies, Vol. 55, No. 3 (Nov., 2001), pp. 233-248 Population Pressure and Fertility in Pre-Transition Thailand

Before the demographic transition in Thailand, fertility was high, but not uniformlys o. As in other pre-transitions ett

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Population Studies, Vol. 55, No. 3 (Nov., 2001), pp. 233-248 
Population Pressure and Fertility in Pre-Transition Thailand

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Population Pressure and Fertility in Pre-Transition Thailand Author(s): Mark Vanlandingham and Charles Hirschman Source: Population Studies, Vol. 55, No. 3 (Nov., 2001), pp. 233-248 Published by: Population Investigation Committee Stable URL: http://www.jstor.org/stable/3092863 Accessed: 28/01/2010 05:02 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.jstor.org/action/showPublisher?publisherCode=pic. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected].

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Population Studies, 55 (2001), 233-248 Printed in Great Britain

Population pressure and fertility in pre-transition Thailand MARK VANLANDINGHAM

AND CHARLES

HIRSCHMAN

Abstract. Before the demographictransition in Thailand, fertility was high, but not uniformlyso. As in other pre-transitionsettings,Thai fertilityrespondedto pressuresand opportunitiescreated by socioeconomic structureand land availability.Drawing upon provincialdatafromthe 1947and 1960censusesof Thailand,we finda strong'frontiereffect' on Thai fertilityin the 1950s.Fertilitywas higherin sparselysettledfrontierprovincesand lowerin provinceswith higherpopulationdensityrelativeto cultivatableland. This findingis robustand holdsup withcontrolsfor agriculturalemployment,landquality,and the sex ratio (an indicator of sex-selectivemigration).The effect of population pressurelowers the likelihoodof marriageand of maritalfertility.The findingsfromThailandareconsistentwith the researchof Easterlinon the nineteenthcenturyUnitedStatesandwithotherpre-transition societies.We suggest how demographictransitiontheory might be broadenedto include societies. fertilitydynamicsin pre-transition INTRODUCTION

The rapid and sustained declines in fertility from about 1870 to 1930 in many Western countries and from about 1960 to the present in many less developed counties have given rise to the theory of the demographic transition. Although there are several variants of transition theory (Davis 1963; Coale 1973), there is broad agreement on the basic empirical features. In response to declines in mortality and the stirrings of socioeconomic development, fertility falls from levels of four to eight children per couple to small families with about two children. Although there are variations in the timing, the conditions required for the onset of fertility change, and in the tempo of the decline, the process is one that is well recognized as one of the major correlates of modernization over the last century (Watkins 1987; Hirschman 1994b; Kirk 1996; Mason 1997). There is, however, much less theoretical attention given to significant fertility dynamics during the pre-transition era. In eighteenth century Europe, for example, fertility is thought to have ranged from about 4.5 births per woman in some countries to about 7.5 births in others (Coale 1974). These very large variations in pre-transitional fertility differentials are often attributed to differences in 'natural fertility' - differences unrelated to conscious motivations to control childbearing.Societies are thought to differ in cultural orientations that influence the proximate determinants of fertility, e.g., marriage, breastfeeding, or abstinence practices. Although a key assumption behind natural fertility may be true - conscious efforts to control fertility are

necessary to produce the sustained and irreversible fertility transitions to the replacement levels found in the modem era - this does not necessarily imply that the wide swings in pre-transition fertility were not a response to social and economic factors. Indeed, the recent research provides much more evidence of continuity in fertility patterns and determinants across pre-transition and post-transition societies than is usually stated in demographic transition theory. In this article, we examine regional variations in fertility during the 1950s in Thailand, about 10 to 20 years before the rapid reduction in Thai fertility began (Knodel, Chamratrithirong, and Debavalya 1987; Hirschman, Tan, Chamratrithirong, and Guest 1994) to test the 'frontier hypothesis'. The frontier hypothesis is an interpretation of how economic constraints - the availability of agricultural land - affects fertility levels in pre-industrial settings. Although the original development of the frontier hypothesis was based on studies of nineteenth century America (Easterlin 1976), it has found support from empirical studies of contemporary societies (Merrick 1978). Extending this work to Southeast Asia provides important insights into the roots of the rapid and sustained fertility declines that began there in the 1970s. Theoreticalperspectives The long-term viability of human communities requires that there be a rough balance between the needs of populations for sustenance and the resources available from the environment. Since the industrial revolution, and especially over the last 233

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century, this elementary postulate has been obscuredby revolutionarychanges in technology andtransportationthatexpandedthe availabilityof food and other resources on an unprecedented scale.Butformuchof humanhistory,technological change moved at a snail'space, if at all, over the centuries.The corollaryof imperceptibletechnological change was that the rate of population growthoscillated,but with a centraltendencyclose to zero. Demographictheory has developedin response to the recentpast - the dramaticchangesin mortality and fertilitythat are known as demographic transitions.These transitionsoccurredin much of Europefrom 1870to 1930and havebegunin much of the less developed world over the last few decades.In contrastto the abundanceof literature on the transition,there is relativelylittle on the demographicdynamicsof pre-transitionsocieties. Kingsley Davis's (1963) version of demographic transitiontheory,which he labelledthe theory of the multiphasicresponse, broadened the demographictransitiontheory'sframeworkto considera wide variety of responsesto increasedhousehold size in both traditionaland modernizingsocieties. These ideas have been elaboratedin articles by Friedlander (1969, 1983) and broadened to a generaltheoreticalperspectiveof populationhomeostasisby Lee(1987)andWilsonandAirey(1999). The central causal variablein Davis's essay is household strain, which is pressurecreated by a growthin householdsizeunderlimitedresourcesor rising expectationsfor economic improvement,or both. In recenttimes,the increasein the probability of offspringsurvivalis the basis for demographic disequilibrium or household strain. Although declining fertility is one response to household strain,this declineis generallythoughtto occurnot through individual conscious control of childbearing (modem contraceptiveshad not been inventedwhen the historicaldeclines began) but rathermore indirectlyvia macro-levelculturaland socioeconomicresponses,suchas changinglevelsof out-migrationor changingnormsaboutthe timing of marriageandterminalabstinence. Other (less dominant) theories give more emphasisto an individual'sor a couple'sassessment of a changing opportunity structure. Richard Easterlin(1976) has pioneeredan empiricalliterature with his work on the effects of population density in settled agriculturalareas and frontier regions in the nineteenthcentury United States (US). In his workEasterlinpositsthatthe priceand availabilityof land will affect decisions about family size when parentsanticipatebeing able to 234

endowtheirchildrenwithresources(land).He finds strongsupportfor thispremisein his analysisof the relationshipsamong land availability,land prices, and fertilityfor six frontierstatesin the US during the 19thcentury.Beanet al. (1990)also findhigher fertilityin frontierareas. Firebaugh(1982) finds a negative relationship betweenpopulationdensityandfertilityin India,as does Merrick(1978) in Brazil, but neither study systematicallyexploresthe key causal mechanism underlying Easterlin'shypothesis about density effects - parents' anticipatedcapacity to endow their offspringwhen they come of age. It is this conceptionof endowmentor 'bequest'that motivates our studyof populationdensityand fertility. Our work also advances this literatureby using census data to study a national rural population,

and by exploringthe sourceof fertilitydifferentials, that is, the extentto whichthe differentialsare due to marriagepatternsor to levels of fertilitywithin marriage.

Thailand provides an ideal setting for an applicationof some of these propositionsabout frontier areas, resourceconstraints,and fertility. Historians have characterizedSoutheast Asia as having densely settled 'pockets of intensive rice cultivation'with an open frontier available for exploitation(Reid 1988;see also Hirschman1994a and Xenos 1994). Migrationto and cultivationof frontierareasin the regionto exploitopportunities for crop exportshavebeen noted at least since the 1600s (Reid 1993); the past century has brought especiallyfavourableeconomicconditionsfor rice cultivationand a rapid expansion of agriculture into previouslyunsettledor sparselysettledareas. Interactions between rural Southeast Asian populations and their environmentswere clearly quitedynamicin historicaltimes(Wyatt1984;Reid 1993),and a numberof studieshavefocusedon the demographyof the region during the premodern era (e.g., Fliegerand Smith 1975;Owen 1987;Reid 1987). While these earlier works have provided valuable insights and stimulating hypotheses, population-baseddata on fertility,migration,and densityare eitherlackingor are highlysuspectfor most of Southeast Asian history. Like Xenos (1994), we see great potential in early moder census data for the systematic analysis of the peopling of the SoutheastAsian frontier,and we exploit this resource in our analysis of pretransitionaldemographicdifferentials. As we explainin detailin the next section,forces having an impact on the relationship between population and environment during the late nineteenthand early twentiethcenturiesincluded

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gradualpopulationincrease,a changein the profitabilityof cultivatingpreviouslyunsettledterritory, and the linkingof theseperipheralterritoriesto the core. The regionexperiencedan explosiveincrease in internationaltrade, resulting in an expanded market for rice exports. Settlement of the surroundingjunglebecameprofitable,albeitconstrained by a lack of sufficientlabour.It is our contention that these demographicand economic changes encouragedmigrationto underpopulatedregions and led to relativelyhigh fertility among the inhabitantsof thesenewlysettledareas. The countrysetting

Thailandliesin theheartof mainlandSoutheastAsia (Figure1), and possessesa fertilecentralplain and riverinedelta,a mountainousnorthand south, and an aridnortheastern plateau.Sincethe establishment of thefirstunifyingkingdomat Sukhothaiduringthe thirteenthcentury,andperhapsevenbefore,the Thai in thevalleysof the populationhasbeenconcentrated ChaoPhrayaRiverandits tributaries, extendingfrom theuppercentralplain,throughthe areasurrounding present-dayBangkok, to the Gulf of Thailand. Exceptfor thesecentralrivervalleysand a few other mostof thecountrywaseither importantsettlements, or unpopulated only verysparselyso untilfairlylate in this century(Wyatt 1984;Arbhabhiramaet al. 1988;Keyes1989). But even if the earlyThai populationwas small by modernstandards,Thai demographichistoryis a dynamicone.TheThaisthemselvesarethoughtto have arrivedin present day Thailand during the periodbetweenthe seventhand thirteenthcenturies A.D. Non-Thai groups who had arrived earlier were displacedor assimilated,and, althoughdata adequateto confirmthis arelacking,the population presumablywaxedand wanedwith the fortunesof the various Thai kingdoms.Numerouswars with Burma must have had dramatic impacts on populationsize and its distribution.The taking of large numbersof prisonerswas common.Warfare must havebeen extremelydisruptiveto agricultural life when populations were so concentratedinto densely settled core areas. Eventually,these wars resultedin a move of the capitalfromAyutthayato Thonburi/Bangkokduring the latter half of the eighteenthcentury(Wyatt1984;Reid 1988;Keyes 1989;Hirschman1994a). The expansion of Thai agriculture

Throughoutthis turbulenthistory and until the latter half of the nineteenth century, the establishmentof densely settled cores with an

unpopulatedor very sparsely populated frontier remainedthe basic Thai settlementpattern. The beginningsof more extensivefrontiersettlementat that time had several causes. In 1855, Sir John Bowring negotiated a major treaty between the British and Siamese which did much to open Thailand'smarketto Britishgoods and helped to make it profitable for investors to ship highly regardedThairiceabroad(Fulleret al. 1983;Wyatt 1984);the growingnumbersof wage labourersin Bangkok also increased the demand for rice (Hirschman 1994a). These changes led to a remarkableexpansionof the transportationsystem linking agriculturalregions in the surrounding countryside to the core Bangkok area, mostly throughcanals,at the turnof the century(Johnston 1976). The majority of land in the Thai central plaincameundercultivationby 1925(Piker1976). The aftermathof WorldWar I brought about higher rates of population growth in Thailand (Piker 1976) and greater demands for Thai rice abroad(Hanks1972).The expansionof landunder cultivationcontinued into the north, south, and northeast, until the disruptioncaused by World War II. After the war, population growth rates peaked at over 3 per cent per year (Piker 1976; and Debavalya1987), Knodel, Chamratrithirong, the expansionof the transportationsystemfurther facilitatedthe linkingof agriculturalareaswith the ports,and the areaundercultivationagainbeganto increase.The railwayto Korat was completedin 1900,to ChiangMaiin 1921,to Khon Kaenin 1930, and to Nong Khaiin 1953.The extensionof the rail networkdid much to expandproduction(Ingram 1971; Fuller et al. 1983), even if the primary motivationsfor railroadconstructionhad more to do with issuesof nationalsecuritythanwith desires to increaseagricultural output(Keyes1989). Before1950therewasno nationalroadsystem,so large-scaletransportwas limitedto areasconnected either by waterwaysor by the railroad. But the expansion of paved roads during the 1950s, and especiallyduringthe 1960s,furtherfacilitatedthe linking of previouslyisolated outlying areas to populationcentres(Ingram1971). With little technologicalchangeoccurring,most of the increased production resulted from an expansionof the amountof land undercultivation, and much of this expansionduringthe 1950s and 1960soccurredthroughthe cuttingof forestlands in the North and Northeast (Ingram1971;Feeny 1988).Keyes(1982),for example,reportsa decline in northeasternforestcoverfrom 62 per cent of all land in 1956 to 27 per cent by 1973.Total land under rice cultivation in Thailand was about 9 235

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Figure1. Title:ThailandandmainlandSoutheastAsia Undermap:Reproduced courtesyof TheGeneralLibraries,Universityof Texasat Austin

million rai (1 rai = 1600 m2) around 1905, 25 million rai in 1946, 39 million rai in 1961, and 48 million rai in 1970 (Ingram 1971; Thailand National Statistical Office 1982). 236

This expansion of land under cultivation was further expedited by longstanding Thai traditions regarding land tenure. In Thailand, uncultivated land has generally been considered to be available

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A study conducted by Chulalongkorn University'sInstitutefor PopulationStudies(1981) found that migrationrates during the late 1960s werehighestamong young adults and werehigher for males than for females.The ratespeak at ages 20-39 for men and ages 10-29 for women. These ages coincidewith the beginningof familyformation in Thailand,and this conceptionis consistent with the reasons migrantsgive for leaving home. Among the reasonscited for rural-to-ruralmoves during the period 1975-80, family reasons were predominantfor both male and female migrants, that is, the move took placebecauseof a changein maritalstatus or to accompanyanotherperson in the household (Goldstein and Goldstein 1986). Goldstein and Goldstein (1986) do not present comparable data for earlier periods, but Prachuabmoland Tirasawat(1974) report on a study, conductedduring the late 1960s, in which marriagewas by far the most commonreasoncited by male migrantsfor movingto theirpresentrural location. Also, a study of a rural Thai village in Khon Kaen province (Fukui 1993) found that, during the period between 1935 and 1964, the primaryreasonsfor migratinginto the villagewere marriageand ook-hien,or the settingup of a new household by a newly married couple; no one migratedin for new land since all land was already occupied. The primaryreason for out-migration duringthe sameperiodwas for new land, followed by marriageand ook-hien.Out-migrantswho left the provincemoved west and northwest,the vast own. majorityto Udon Thaniin the upperNortheast. Interprovincialmigrationduring the late 1950s Migration duringthe 1950s and 1960s and late 1960s was primarilyintraregional,with In Thailand, the 1950s and 1960s were charac- migrantsrelocatingwithin the Northeastcompristerizedby moderatelevelsof interprovincial migra- ing the largest single migrant stream during tion. In 1960, 11 per cent of the Thai population both periods. But after intraregionalmigration, were not living in their province of birth, and individuals from the densely settled Central this proportionincreasedto 13 per cent by 1970. region (excludingBangkok)made up the majority In 1960, recent interprovincialmigration(during of migrantsto all three outlying regions during the previous5 years)was reportedby 3.6 per cent both periods(GoldsteinandGoldstein1986). To summarize, during the 1950s substantial of the Thai population over age 5; this figure rose to 5.9 per cent by 1970 (Goldstein and numbersof young Thai men and women,many of them recently married, were migrating between Goldstein1986). Migrationfrom rural areas to Bangkokduring ruralareas.Many of these migrantswere moving these two decadeswas substantial,and this feature fromthe denselysettledCentralregionof Thailand, and some moved with the intentionof setting up of Thaimigrationhas receivedthe most attentionin the literature.But the majorityof interprovincial new households.An absenceof strictregulationof land tenure allowed for the homesteading of moves in Thailand (63 per cent according to calculationsby Goldstein and Goldstein (1986)) unoccupiedlandwhereit was available.Wewillnow duringthe late 1960s (and presumablyduringthe investigatewhetherthese migrationpatternswere 1950s as well) were rural-to-rural moves; associated with higher fertility in the receiving rural-to-urbanmovescomprisedjust 11 per cent of areas, as would be predictedby a frontiereffect framework. the total.

to whomeverwould clear and maintain it (Piker 1976). Accordingto the Land Acts of 1936 and 1980, Thais were allowed to clear and cultivate unused land (usuallyup to 25 rai), but the King could reclaimthe land if it was left fallowfor three years(Ingram1971). Eventually,homesteadingbecomesmoredifficult (or 'expensive') as land becomes more scarce, marginal, and legally regulated.The 1901 Land Lawwas an earlystep in conceptualizingland as a 'legal commodity' (Keyes 1976), but the idea of land being freely availableto those who would cultivateit still exists in modern times. Marzouk (1972)reportsthatthe landcode currentat the time made provisionsfor squattersby issuinga 'reserve license,'but overhalf of the land undercultivation in Thailand at that time did not even have this modicum of legal status. Arbhabhiramaet al. (1988) reportthat in 1986 only 63 per cent of all cultivatedland was coveredby either land title or certificateof utilization. Homesteadingof unoccupiedland in Thailand has often been undertaken by newly formed families.In the ideal, a newly marriedrural Thai couple will reside first with the bride's parents (Fukui 1993). If the bride'sparents'farm is large enough, it will be subdividedamong her and her siblings.If it is not largeenough to subdivide,the youngestdaughterand her husbandwill inheritthe house and farmwhileher siblingsmust accumulate enoughcapitalto set up a house and farm of their

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the frontiercan. The followingare among omitted provinces:Bangkokand Thonburi,whichcomprise Data Bangkok proper;Samut Sakhor, which is very We focus on the 1950sfor severalreasons.First, as near Bangkok and is relativelyhighly urbanized; noted in the previous section, this was a period and SamutPrakan,which is adjacentto Bangkok and is very denselypopulated.Omissionof these characterized by considerable migration to relativelyunderpopulatedareas.Second,the 1950s greaterBangkokprovincesremoves9.7 per cent of predatethe introductionof contraceptivesand the the total 1960 population. We also omit the fertilitydeclinethat sweptthroughThailandduring following: Mae Hong Song, located in the thelate 1960sand 1970s(Knodel,Chamratrithirong, northwestcorner of the country, because of its andDebavalya1987),a factthatservesourobjective implausiblylow levelof fertilityfor the early 1950s of investigatingfertilitydifferentialsexistingbefore (most probably due to underenumeration);the the introduction of modern means of fertility southern island of Phuket because of the high regulation.Third,datacollectedfor the 1960census proportion of municipal residents (37 per cent) are the earliestavailablethat allow us to estimate and, as in Bangkok,associatedincreasedopportufertilitylevels and a numberof predictorvariables nities for nonagriculturalemployment; Samut at the provinciallevel.We also drawextensivelyon Songkram,just south of Bangkok, because it is publishedstatisticsaboutthe amountof landunder extremelydensely populated (826 persons/square cultivationin each provinceduring this and later kilometerof potentiallyarableland) and because marinefisheries,which should not be affectedby periods. An analysisof provincial-leveldata for a study populationdensitiesin the same manneras landsuchas this has a numberof disadvantages.First,it based agriculture,constitutes a central industry; restrictsthe numberof data points in our analysis. Kalasin, in the Northeast, because we cannot Second,aggregationto the provinciallevelobscures estimateits populationin 1947(it did not yet exist variationswithin provinces(e.g., among amphurs, as a separateprovince);and the four southernmost or districts). For example, provincial-leveldata provincesof Yala, Pattani,Narathiwat,and Satun makeit impossibleto distinguishurbanfromrural because they are culturally and demographiareas within provinces.Goldstein and Goldstein cally distinct from the rest of the country. See (1986)estimatethat limitingmigrationestimatesto VanLandingham and Hirschman (1995) for more details. The remaining 59 predominantly interprovincialmoves capturesonly about half of those who wouldbe identifiedby usinga definition ruralprovincesinclude85 percent of the total 1960 of changein residence.Unfortunately,the required Thai populationand 92 per cent of the total land dataarenot availablefor geographicalunitssmaller area. thanprovinces. Reliablelongitudinaldata would be superiorto Measures the cross-sectionalmeasureswe employ,since our hypothesesaddressprocessesoccurringover time. Our estimatesof provinciallevels of fertility are We attempt to capture some features of the basedupon the Relemethod(Rele 1967,1989).The historical nature of these phenomena in our Rele method estimates total fertility (TF) from measureof populationdensity,butwe believethata child-womanratios(CWR)in each provinceand a of the of the Thai measure of mortality(nationallife expectancyat truly longitudinalstudy filling frontier would face serious problems of data birth).The methodproducesfertilityestimatesfor quality;as noted above, we believe that the 1960 the period0-4 yearsbeforethe censuswith a CWR Thaicensusdataarethe earliestreliabledatafor the utilizing children 0-4 years of age and married womenaged 15-49;fertilityestimatesfor the period requiredoutcomeandpredictorvariables. Weuse data from 59 of the 71 provincesexisting 5-9 yearsbeforethe censusemploya CWRutilizing in Thailandduringthe period of study.Since our children5-9 yearsof age and marriedwomenaged 20-54. hypothesis concerns the effects of resources on For the period 1955-59, the Rele method areas,we omit fourprovinces fertilityin agricultural nearBangkok.Highlyurbanizedareaswill provide producesa lowerestimateof TF than that derived opportunitiesand constraintsthat aredistinctfrom froma stablepopulationestimationprocedure(see those found in rural areas. For example, the VanLandinghamand Hirschman1995for details). Bangkok area will provide wage employment We conclude that the Rele method results in an opportunitiesthat are unlikelyto encouragehigher underestimateof fertilitybecauseof an undercount of childrenaged 0-4 in the 1960Thai census.Rele fertilityin ways that agriculturalopportunitieson METHODS

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(1989) acknowledges this shortcoming of the method. Children aged 5-9 are less subject to underenumerationin censuses.The Rele estimateof TF for the period 1950-54using childrenage 5-9 and women20-54 is 6.2, whichis muchmoreconsistent with the stablelife tableproceduredescribedabove. Thus, we will focus our analysis on the earlier period(1950-54),sincewe havemoreconfidencein theseestimatesof provincialfertility. Our density measure is designed to assess the perceivedcarryingcapacityof the landas viewedby individualsliving duringthe periodcoveredby the study. As our index of population pressure,we compute provinciallevels of population density usingthe 1947censusenumeratedpopulationin the province(ThailandNationalStatisticalOffice1976) divided by the amount of land in the province under cultivation in 1978 (Thailand National StatisticalOffice1982).The 1947populationis used becausethis providesthe most currentestimateof the population in each provinceduring the early 1950s.The land undercultivationin 1978is used as an estimateof the amount of land that could be brought under cultivationduring the subsequent generation.The year 1978representsapproximately one generation (23-28 years) after the birth of children during the period of interest (the early 1950s). We use 1978 as a referencepoint for two other reasons.First, it appearsto be a typical year,and second,the total areaundercultivationis available. The early1970sseemveryatypicalsincetherewas a drop in the number of rai planted in rice. We recalculatedthe associationsbetweenfertilityand our densitymeasureusing the area plantedin rice for other typical base years (e.g., 1968 and 1976) and obtainedsimilarresults. There are several alternatives for measuring populationpressureandwe chosethe one described aboveprincipallyon theoreticalgrounds:giventhe data availableto us, we feel it best capturesthe future potential for agriculturalexpansion. Our conceptualizationof populationpressureis consistent with measuresused by Easterlin(1976) in his study of the American frontier. For example, Easterlinpresentsthe actual-improved acreageas a percentageof ever-improvedacreage to approximatethe degreeto whicha frontierareahas become saturated.Wepresentthe actualpopulationsizeper unitof landthatis cultivatedone generationhence. Weemployfouradditionalindependentvariables in the multivariateanalysis.First,the proportionof the population living in agriculturalhouseholds (fromthe 1960Thai Census)is includedas a proxy

measure for the availabilityof nonagricultural employmentopportunitiesin the province.This variable controls for some of the effects of modernizationon fertilitydifferentials.Second,we include a measure of the quality of agricultural land to accountfor the fact that not all agricultural land is equally productive.Because land in some areas will be capableof supportingmore individuals per unit than others, the inclusion of this control variableis necessaryto better specify the relationshipbetweenavailableland and fertilitynet of variationsin land quality.We approximateland qualityin eachprovinceby a measureof the average numberof kilos of rice producedper rai of land under rice cultivationin 1960 (ThailandNational StatisticalOffice1963).Third,we includea measure of the sex ratio of young adults (males 20-29/ females 15-24) from the 1960 Thai Census to controlfor differencesin the degreeof competition for wives.We expect that in areaswherethereis a shortageof marriageablewomen, overall fertility will be highersince each woman will have greater opportunitiesor pressureto marry early; Guest (1990)takesa similarapproach.The proportionof women aged 20-54 who werecurrentlymarriedin 1960 (according to the 1960 Thai Census) is includedas an interveningvariableto capturethe effects of local marriagepatterns(entry into and dissolutionof marriage)on total fertility. Procedures

We begin with an illustration of the bivariate relationship between population density and fertilityfor the 59 Thaiprovincesusinga scatterplot and a series of Thai provincialmaps shaded for these variables.The second step is to estimatethe effect of density on fertilitynet of the effects of nonagriculturalopportunities,the quality of the agriculturalland, and differencesin the pressures and opportunitiesavailablefor young women to marry.We pursuethis second step by using probit and least-squaresmultivariateregressionto control simultaneouslyfor these potentially confounding factors. In the final step, we decomposethe total effect of density on fertility into marriage and maritalfertilitycomponents. Hypotheses

Figure 2 outlines our proposed model of how populationdensityaffectsfertility,andincludestwo control and two mediatingvariables.Our control variablesare the proportionof agriculturalhouse239

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RESULTS

Description of the data

Figure 2. Title: Relationships between variables in a frontiereffect model of the determinants of pre-transition fertility

holds (a proxyfor modernization)and land quality. We anticipate a strong negative relationship betweenpopulationdensity and fertilityonce the potentialmaskingeffectsof thesetwo variablesare controlled. This central hypothesisis interlinked with two other expectedresults.First, we expect that sparsely settled frontier areas will attract migrants who wish to profit from the growing demandfor Thai agriculturalproducts.Second,we expectthatindividualslivingat the frontierwill face lower costs for childbearingthan parentsliving in more denselysettledareas,becausetherewill be a shortageof labourthat can be alleviatedto some degreeby childbearing,and becauseparentsat the frontier will anticipate better prospects for endowingtheirchildrenwith landthanwill farmers in moredenselysettledareas. Thetwo interveningvariablesin the modelarethe sex ratioof youngadultsandmarriagepatterns.We anticipatethat some of the effectsof densitywill be mediated through high male/female sex ratios. Where migration results in more marriageable malesthan females,therewill be increaseddemand for women to marry early or begin childbearing early in the marriage,or to do both. And where thereis earlymarriageand childbearing(eitheras a consequenceof these high sex ratiosor becauseof more ampleresourcesin low-densityareas),period fertilitymeasureswill be higherthanin areaswhere familyformationis late. Finally,we anticipatethat density may affect fertilityvia marital fertility(a 'direct'effect in this diagram).In frontierareas, familieswill desire more childrenthan in densely settled areas, thus increasingfertilitywithin marriage.However,since moder methods of fertility control are not availablein this population, we anticipatethat the main effects of density should work throughmarriagepatterns(especiallyage at marriage) rather than through within-marriage fertilitycontrol. 240

The measuresused in the analysisare describedin Table 1. The firstcolumnprovidesthe mean value of eachvariablefor all 71 Thaiprovincesat the time of the 1960census.The remainingcolumnsprovide the meansand rangeof the variablesfor the subset of 59 provincesused in the multivariateanalysis. The range of provincial-leveltotal fertilityfor the latter group is about a child and a half. Total fertilityfor Bangkokand Thonburi,whichare not included in the multivariateanalysis, is approximately5.8 births,but the lowestlevelsoccuramong the excludedsouthernmostprovinces(we believe the 4.8 levelfor Mae Hong Song to be the resultof minorsevereundercountsof the difficult-to-access ity groupsin thatremotemountainousprovince). Populationdensityvarieswidely,froma low of 22 personsper squarekilometerof potentialfarmland in sparselysettledKamphaengphetprovincein the lower North (just south of Tak in Figure 1), to a high of 1,438in Bangkokproper.The most densely settled province in the multivariateanalysis is Lamphun(just south of ChiangMai) in the upper North, with 386 persons per squarekilometerof potential farmland.All the provincesincludedin the analysis have at least 54 per cent of their populationsliving in agriculturalhouseholds,but agriculturalproductivitycoversa broadrange.The most productiveareasarein the North and Central regions, while the least productiveprovincesare locatedin the morearidNortheast. The averagesex ratio of young adults is about even for men and women (0.93) but rangesfairly widely among the provinces.Sex ratios tend to be high(moremen)at the extremelevelsof population density.There is also a fair range of proportions married(69 per cent - 86 per cent) among these ruralprovinces. Bivariateanalysis

If our depiction of frontiereffects on fertility is correct, we would expect a plot of fertility by density in rural areas to reveal a negative relationship,that is, fertilitylevels should decrease with increasingdensity.This is preciselywhat we find in the resultsdisplayedin Figure 3. Sparsely settledareaswith high levels of fertilityare in the upperleft of the plot, and denselysettledareaswith low fertility are in the bottom middle and lower right of the plot (r =-.56;

p = 0.0000). This

associationbetweenpopulationdensityandfertility is even more compelling when the positions of

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usedinananalysisof theeffectsof populationdensityonfertilityin Thailandin theearly Table1. Meanvaluesandrangeof thevariables 1950s.

Variable Totalfertility1950-54 Populationdensity Proportionlivingin agricultural households Landquality Sexratioof youngadults Proportionof womenmarried

N = 59provinces

N= 71provinces mean

mean

Minimumvalue

Maximumvalue

6.1 180 76%

6.2 132 79%

5.5 22 54%

6.9 386 94%

237 0.93 76%

237 0.93 76%

81 0.75 69%

476 1.31 86%

Notes:Totalfertility1950-54is a Releestimationfortheperiod1950-54. Source:1960Thai Census;UN 1993. Populationdensityis the 1947population/ the numberof squarekm undercultivationin 1978. Sources:1947Thai Census;ThailandNational StatisticalOffice1982. Proportionlivingin agriculturalhouseholdsis the proportionof the populationliving in agriculturalhouseholdsin 1960. Source:1960Thai Census;ThailandStatisticalOffice1963. Land qualityis the averagenumberof kilos of riceproducedper rai of land. Source:ThailandNational StatisticalOffice1963. Sex ratio of young adultsis the numberof men age 20-29 / the numberof womenage 15-24. Source:1960Thai Census. Proportionof womenmarriedis the proportionof womenage 20-54who arecurrentlymarriedin 1960. Source:1960Thai Census.

individualprovinceswithinthe plot areconsidered. As expected, the long-establisheddensely settled provincesof the lowerChao Phrayarivervalleyare in the bottom middle-rightof the plot, while the sparselysettledprovincesof the North, Northeast, and South,arein the upperleft. The cluster of four northernprovincesin the bottom right of the plot can also be interpreted using our paradigmof frontiereffects.While the North as a region was a major destination of migrantsduring this period, these four provinces had among the lowest proportions of recent migrantsin 1960(0.8 per cent to 1.5 per cent).Two of the provincesare long-establishedareas(Chiang Mai and Lampang)with probablylittle room for additional agriculturalexpansion. The other two (Phraeand Nan) are mountainousprovinceswith likewiselittle room for expansion.Indeed,all four provinceshad veryhighdensitiesof populationper area of potentiallyarableland (between312 and 381personspersquarekilometer). These interrelationships among fertility,density, and expansionof the frontierarefurtherillustrated in Figures 4-6. Figure 4 is a map highlighting provinceswith relativelylow population density during the late 1940s and early 1950s (lightly shaded); these are the provincesthat had small populationsin 1947giventhe amountof land that would be undercultivationby 1978.Thesesparsely settledprovincesoccupya swatheacrossthe middle of the country. The most densely settled areas

(shaded dark) include the cluster of long settled provincesof the lower Chao Phrayaand Suphan Buririverbasins,just north and west of Bangkok, and much of the mountainousupper North. The otherprovincesof the lowerCentralplain,most of the southern peninsula, and the easternmost provincesof the Northeast had moderatelyhigh density duringthis period;the latter group in the late 1950shad among the lowestrice yields per rai in the country(ThailandNational StatisticalOffice 1963).Thesedenselysettledareasprobablydid not afford much hope for further agricultural expansion.

But there were opportunities for agricultural expansionin the sparselysettled provincesacross Thailand'sas-yet-undevelopedheartland.Figure 5 shows that these frontier provinces were the preferreddestinationsof manymigrantsduringthe late 1950s.MetropolitanBangkokis also clearlyan important destination, but it is omitted from consideration in our statistical analysis since individualsmigratingto Bangkokalmost certainly went seeking opportunitiesin the modern urbanbased economy rather than for any perceived opportunitiesin agriculture.As discussed in the introduction,most of the migrationin Thailand duringthis periodwas rural-to-rural,and this fact is reinforced by the large number of rural destinationsfor interprovincial migrantsduringthe late 1950s. Figure 6 demonstratesthat many of these sparsely settled provinces receiving large 241

MARK

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VANLANDINGHAM

HIRSCHMAN

CHARLES

* Loei

6.825* Udon.Prachuap Kamphaengphet * Phichit * 6.650e Krabi ? Khon Kaen

Kan.Phitsanulok ? Petchabun.Rayong* ?

* Trang

6.475 -

* S

*

: *

6.300-

*

S S *?

6.125-

s Lamphun

S .

*

*

0

*

5.9500

* Phetchaburi

5.775 -

* Ayutthaya 0

SSinghburi

* Angthong .

5.600-

*

*

* Tak

Lampang

ChiangMai Phrae Nan

S

SI 0

50

100

150

200

250

350 400 300 Populationdensity

Figure3. Title:Bivariateplot of populationdensityandfertilityin Thailandduringtheearly1950s. Source:Thaicensusdata

numbers of migrants were among the provinces with the highest fertility during the early 1950s. While the correspondence is not perfect, this series of maps illustrates the great degree of overlap among the provinces having high potential for agricultural expansion, high in-migration, and high fertility. The maps graphically present some of the broad patterns of migration and fertility during this period, but they are limited to the display of bivariate relationships among categorical variables. That is, the maps do not incorporate the potentially confounding influences of other processes that were occurring simultaneously,e.g., differentialmigration by sex, employment opportunities arising in the modern urban-based economy, and variations in land quality. We assess the influence of these factors, and explore the sources of the fertility differentialsin rural areas, in the next section. 242

Multivariateanalysis Multivariate analysis of the effects of density on fertility, including the control and intervening variables described above, is shown in Table 2. Table 2a displays the effects of the predictor variables on the proportion of women aged 20-54 who were currently married in 1960. The outcome variable in these models is a proxy measure for marriage patterns (and exposure to pregnancy) during the early 1950s. These results reveal a significant bivariate relationship between density and marriage patterns (Model 1), and demonstrate that the relationship becomes stronger and more significant as controls are added for agricultural households and land quality (Model 2), and the intervening effects of sex ratio (Model 3) are included. The controls and intervening factor all have effects in the expected directions, and their

POPULATION

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o

140 to 1438: high (26) g 97 to 139: moderate (25) | 21 to 96: low (23) E::

Thailand,late 1950s. Figure5. In-migration, Source:Thaicensusdata

Figure4. Populationdensity,Thailand,early1950s. Source:Thaicensusdata.

F

6.4-6.9: high (23) El. 4.8 - 6.4: low to medium (51) | |

0

miles

200

k

0

km 200

Figure6. Totalfertilityin Thailand,early1950s. Source:Releestimates,using1960ThaicensusandUN 1993

243

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Table2. Multivariate analysisof theeffectsof populationdensityonfertilityin Thailandintheearly1950s onproportion (a)Probitmodelsof predictorvariables of womenaged20-24whoweremarried,Thailand,1960 Proportionof womenage20-54 who aremarried Predictorvariables Log populationdensity Log proportionlivingin agriculturalhouseholds Log land quality Log sex ratio of young adults (menper woman) Significanceof Pearson'sgoodness of fit chi squarestatistic (N)

b b/se b b/se b b/se b b/se

Model 1

Model 2

Model 3

-0.15 -53.6

-0.20 -63.9 0.16 11.8 0.37 90.2

-0.23 -71.3 0.58 40.0 0.23 51.3 1.33 90.4

0.000

0.000

0.000

(59)

(b) Linearregressionmodelof theeffectsofpredictorvariableson totalfertilityin Thailand,1950-54 TotalFertility1950-54 Predictorvariables Populationdensity(*1000)

unstd b std beta p

Model 4

Model 5

Model 6

Model 7

-2.2 -0.56 0.0000

-2.1 -0.54 0.0000

-2.2 -0.55 0.0000

-1.2 -0.31 0.01

Proportionlivingin agricultural households

Land quality Sex ratio of young adults (menperwoman) Proportionof womenmarried (age 20-54) AdjustedR squared Significanceof F test (N)

unstd b std beta p unstd b std beta p unstd b std beta p unstd b std beta p

0.46 0.12 0.29 0.00034 0.07 0.52

30% 0.000

30% 0.000 (59)

0.72 0.20 0.12 0.00016 0.03 0.77 0.50 0.18 0.16

31% 0.000

-0.013 -0.004 0.98 -0.00054 -0.11 0.28 -0.54 -0.19 0.17 5.1 0.60 0.0001 48% 0.000

Notes. The sampleincludes59 of the 71 provincesexistingin 1960.ExcludedprovincesareBangkok,Thonburi, SamutPrakan,SamutSakhorn,Phuket,SamutSongkram,Mae Hong Song, Kalasin,Narathiwat,Pattani, Satun,and Yala.Variabledefinitionsand sourcesof data arereportedin Table1.

predictive power indicates the importance of including these variables to determine the full effectsof densityon marriage. The modelsin Table2b presentthe effectsof the predictor variables, including the effects of marriagepatterns, on the Rele measure of TF during the early 1950s. Model 4 in this table displays the gross effects of density on fertility, Model 5 presentsthe effectof densitynet of the two controlfactors(proportionin agricultureand land 244

quality),and Model 6 includesthe additionaleffect of the interveningvariablesex ratio. Measuresof the proportionin agriculture,land quality,and the sex ratio of young adults are all important predictorsof marriage,but not of fertility.Also, the effectof densityon fertilityremainsquiteconsistent with the inclusionof the control and intervening factors.It is only in the finalmodel(Model7), with the inclusionof marriage,that the directeffect of densityis attenuated.About 55 percentof the effect

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of density on fertility is direct on marital fertility and most of the remainder (43 per cent) is indirect through marriagepatterns (Table 3).

Table3. Directandindirecteffectsof populationdensityon fertilityfromthe linearregressionanalysis

Variable

Total effect

Indirecteffectvia: Direct effect marriage -0.24 -0.31

DISCUSSION

density -0.56 Population

Models including measures for the potential confounding influences of land quality, modernization, and sex ratio imbalances indicate that variations in population density affected fertility in rural Thailand during the early 1950s. Our central finding is consistent with empirical results from studies of population density and fertility in Brazil and India, and it verifies a central hypothesis regarding frontier effects that we derived from studies of the peopling of the American frontier. Our multivariate model is also supported by a series of maps we present to illustrate the areal relationships among population density, migration, and fertility, by a bivariate plot of fertility and density levels among the provinces in our analysis, and by other research focusing on Thai migratory patterns during this period. Earlier work on Thai migration supports our contention that many young Thai couples migrated to areas where there appeared to be opportunity for agricultural expansion, and setting up new households seemed to be a primary motive. The long-established densely settled central region provided a large proportion of the young migrants, and the major streams went to rural areas. We anticipated that density would affect fertility primarily through marriage patterns. We were surprised, however, to find that most of the effect of density (about 55 per cent) is not accounted for by the path through marriage patterns, but rather appears to influence fertility directly. We consider four possible explanations for the surprisingly important role of fertility within marriage. First, there may have been more control of fertility within Thai marriage during this period than we anticipated. Even though modern means of fertility control were not available at this time, couples may have been able to control their level of childbearing within marriage through abstinence or withdrawal. A second consideration is that these withinmarriage effects could be due in part to differential impacts of spousal separation as a result of seasonal migration, if seasonal migration was more common in core than in frontier areas. Since enumeration is de jure, it is unlikely that our sex ratio measure would control adequately for this. However, although seasonal migration is a common employment pattern for Thai men in more modern

Note.Displayedeffectsarestandardized betacoefficients. times, it is very doubtful that either Bangkok or the frontier areas would have held much opportunity for extended seasonal employment for large numbers of men residing in the core agricultural areas during the 1950s. Third, our measures of the influence of marriage on fertility could be confounded by other factors. In particular, unlike an actual TF, the Rele procedure could be influenced by differences in female age distributions. If some provinces had higher proportions of women in prime reproductive ages than other provinces, fertility differentials among provinces could be due to differences in age structure. We examined whether the proportion of women in prime reproductive ages (i.e., the proportion of women age 20-29/women age 15-49 at the end of the period of interest) was correlated with fertility and found that it was not. Another problem with our measure of marriage that we are unable to explore further is that the proportions married in 1960 do not perfectly reflect exposure to childbearing during the first half of the 1950s, when these children were actually born. However, it is difficult to imagine scenarios in which our measure of marriage would not provide an adequate proxy measure for exposure to childbearing in the same area earlier in the decade. Fourth, since many of the persons migrating to Thai frontier areas were already married, this probably served to lessen the degree to which marriage patterns could affect fertility in the frontier environment. The fact that marriage does play a substantial role apparently reflects the extent to which marriage patterns affected the fertility of second-generation or subsequent-generation migrants and first-generation migrants who were single when they moved. The limitations of the marriage variable thus serve to make the overall observed fertility differentials even more remarkable. After considering these alternative explanations, we conclude that a surprising amount of control of fertility within marriage is apparent. We speculate that some degree of the regional variations in marital fertility between the frontier and denselysettled areas could be due to changes in coital 245

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activitythat may be relatedto perceptionsof the abilityto supporta largefamilyand to bequestland to children.Even if the changes in behaviourare not conscious in the modem sense of decisionmaking,it seemsthat the behaviouralchangeswere motivatedby externalconditionsthat affectedthe economicwelfareof familiesandtheirprogeny. This interpretationmay be at odds with some versionsof demographictransitiontheory,but the findingsareconsistentwith othertheoreticalframeworks.Overall,our empiricalfindingscorrespond extremelywell with Easterlin'sbequestmodel.Thai parentsin the early1950sappearto haveconsidered the availabilityof agriculturalland one generation hencein theirchildbearingdecisions.But a possible alternativeexplanationis Caldwell's(1989) wealth flows hypothesis,whichis often invokedto explain fertilitydifferentials.It followsfroma wealthflows perspective that children may be particularly valuableto parentsin frontierareasbecauseof the labourthey provideto parents;also, childrenmay be more expensive to parents in more densely settled areas because of the costs of education. Both of these possible mechanisms should be diminished substantiallyby our elimination of urbanized areas from the analysis, and by our controlformodernization. To explore furtherwhetherlow levels of child educationmightinflatefertilityin frontierareas,we employeda proxymeasureof the extent of childhood educationin eachprovince:the proportionof 10-year-oldchildren having no education. While therewas substantialvariationamongprovinceson this variable(3-17 per cent), this measureof the extent of childhoodeducationwas not associated with eitherdensityor fertility.A wealthflows perspectivethus fails to explainadequatelythe fertility differentialsfoundbetweenThailand'sfrontierand coreruralareas. We conclude with three caveats resultingfrom shortcomingsin the historical data we employ. First,sincewe measurefertilityindirectlyby adjusting child/woman ratios, differential childhood mortalityis a potentialsourceof variationin our fertility measure. A related problem is possible differentialundercountingof young children.It is quitelikelythatdifferentialmortalityand enumeration do exist among the ruralprovinces,but these processes almost certainly serve to make our estimates conservative rather than overstated. Childhood mortality and underenumerationare veryprobablyhigherin frontierareasthan in longestablished regions, so adjustments for these undercountswould probablymake our reported differencesin fertilityevenstronger. 246

A second issue involves the extent to which parents were able to foresee future prospectsfor agriculturalexpansion.To the extent that increasing technologybringsmarginalland undercultivation, especiallyvia irrigation,one might arguethat parents could not have anticipatedwhich areas wouldexperienceagriculturalexpansionduringthe subsequentgeneration.For example, there were several large dams built in Thailand during the 1960s and 1970s,which probablycould not have been anticipatedduringthe early 1950s.However, theselarge-scaleprojectswerein areasperipheralto the Thaiheartlandwherethe majorexpansiontook place. Ultimately,the questionof whetheryoung Thai adultsin the 1950swereableto anticipatethe future availabilityof land is an empiricalone. Ourresults, basedupon multivariateanalysisof nationalcensus and agriculturaldata, indicatethat not only were they indeed able to do so, but that they were also able to adjust their fertilitydecisionsaccordingly. This conclusion is consistent with earlier studies that discount the potential role of unanticipated technologicalchange. Ingram(1971), focusing on the period ending in the 1950s,has demonstrated that it was expandingcultivationand not technology thatled to the increasein Thai riceproduction. This undoubtedly began to change somewhat duringthe 1960s,and althoughwe recognizethat farmers could not have been aware of future technologicalchange,they apparentlywereable to predictwhich areas held promisefor agricultural expansion,a key assumptionof our model that is stronglysupportedby the empiricalresults. A thirdissueinvolvesthe difficultiesof separating the effects of rural populationpressurefrom the forcesof modernization.Onemightask:Whatwere the migrants seeking by moving?The two most plausiblealternativesappearto be that their aims were 1) to exploit availableagriculturalland at the frontier,and 2) to take advantageof occupational opportunitiesarising from modernization.While both phenomena were occurring in Thailand duringthis period, our thesis revolvesaroundthe firstmechanism.Weattemptto removemost of the effects of the second by omitting the Bangkok metropolitanareaand a few otherhighlyurbanized provincesfrom the analysis.This solution is not entirelyadequatesince our provincialaggregations containurbanareaswithinthem. Keyes (1976),in fact, arguesthatthe primaryresponseto population pressurein the Northeastwas not migrationto the frontier,since by the 1930sthe remainingland had but marginalagriculturalutility (see Ingram 1971 for an alternativeview), but rather growth in

POPULATION

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nonagriculturalemployment.And he is undoubtedly correctto some extent, given the substantial migration streams to Bangkok and some other urbanareas. This issue is also problematicin studies of the Americanfrontier.Easterlin(1976)findsa strongly positive relationshipbetweenland availabilityand fertilityin New YorkStateduringthe earlypart of the 19th century,althoughGuest (1990) finds that by the mid-19thcentury,land availabilityhad little relationshipwith fertility in this state; economic well-being,education,and Baptistreligiousaffiliation were all inversely associated with various measuresof fertility.By the mid-19thcentury,New York had little land available for agricultural expansion;the frontierhad been filled. It is at this point thatforcesof modernizationarelikelyto take hold, and the generalnegativeassociationbetween fertility and affluencewill become apparent.We believethat this processwas beginningin Thailand during the 1950s in areas where the frontierhad alreadyfilled,especiallyin the denselysettledareas aroundBangkok.But it is veryunlikelythat during thiserasubstantialopportunitiesexistedformoder sector employment,especiallyfor the young Thai adults living in the provinceswe include in our analysis(seeTable1). It is admittedlydifficultto answerdefinitivelythe questionof what the migrantsdid upon arrivalat their destinations,since we do not have occupational data. However,since most of the migration duringthis period was rural-to-rural(especiallyin our subsample,since we omit Bangkokand some otherurbanareas),we concludethat most of them musthavebeenengagedin farming.And sincethere was much expansionof land under cultivationin the areas of high in-migration,concurrentwith relativelyhigh fertility,we also concludethat much of the negative relationshipbetween population densityand fertilityfound in these ruralprovinces can be best explained using a frontier-effect paradigm. This conclusion has importantimplicationsfor classicdemographictransitiontheory,as well as for theoriesemphasizingthe innovationand diffusion of new ideas about fertility control. If married couples are able to adjust their childbearing outcomesto a givenopportunitystructure,assumptions about naturalfertilityregimesexistingbefore the demographictransitionmust be reconsidered. ApparentlyThai couples moving to the frontier were able to adjusttheir behaviourin such a way that led to increased fertility, vis a vis the levels

found in the sending core areas. Whether these behavioralchanges involved conscious decisions

about the frequency,timing, or nature of coital activity,we do not know.But whateverthe mechanism was, the differentialsreportedhere belie the widely held assumptionthat, beforethe adventof moder contraceptives,variations in family size werecompletelydeterminedby traditionalcultural norms about intermediatevariablesunrelatedto fertilitygoals. NOTES Mark VanLandingham is at the Departmentof International HealthandDevelopment,Schoolof PublicHealthandTropical Medicine, Tulane University, New Orleans, and Charles Hirschmanis at the Center for Studies in Demographyand Ecology, Sociology Department,University of Washington, Seattle.This workis supportedby a grantto the authorsfrom NICHD (grantnumber1F32HD07687).The paper has been improved by comments of participantsin the population seminarat the Centerfor Studiesin Demographyand Ecology, Universityof Washington.The assistanceof Yih-JiinYoung, Thang Minh Nguyen,Nancy Morrow,and SekarThiagarajan with the maps, and the comments of Avery Guest, Sidney Goldstein,Nancy Grandjean,Ronald Rindfuss,Lea Trujillo, Sara Curran,and CharlotteColvin on an earlier draft are gratefullyacknowledged.An earlierand longerversionof the paperwas presentedat the annualmeetingsof the Population Associationof Americameetingsin San Francisco,1995; a revised version can be found at the Center for Studies in DemographyandEcologywebsite:http://csde.washington.edu

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