Supposeonthesametenantfarmanadditionalcrop,saysoybeans,wasaddedtotherotationafterthesharerestriction,resultinginariseincroparea.Thecrophectareyieldoftheaddedsoybeancropwouldlikelybelowerthanthatofanotherfarmwheresoybeanshadbeenintramarginal.Thereasonisthatiftheraisingofsoybeansonthistenantfarmhadbeenconsistentwithwealthmaximizationunderafreemarket,theywouldhavebeengrown.Thatis,iftheaddedsoybeansreceivedthesameamountofinputpercropareaasonanotherfarmwheresoybeanshadbeenintramarginal,theaddedcroponthetenantfarmwouldhavealowerhectareyield.However,iftheaddedsoybeancropreceivedsufficientlyhighdensityofplanting,itsyieldstillmightbehigherthanelsewhere.Intheaggregateddataavailable,wewouldfindariseinthecropareaofsoybeans,buttheaverageyieldpercropareamightriseorfall.
Suppose,however,thatthistenantfarmcontinuedtosqueezeinadditionalcropsforannualrotationoverafixedareaofland.Therewouldeventuallybeacropwhich,regardlessofplantingdensity,wouldhaveaconsiderablyloweryieldpercropareathanelsewhere.Thisissobecausethebetterlandwouldbeexhausted,thesoildepleted,theseasonunfit,andtheplantingcongested.Thelastcropwhichthetenantfarmsqueezedintotheannualrotationwouldbethemarginalcrop.Thisdoesnotmean,ofcourse,thatalltenantfarmswouldgotothisextremeunderthesharerestriction.Thegeneralideaisthatacropwhichwasaddedatthemarginwouldhavealoweryieldpercropareathanthesamecroponanotherfarmwhereithadbeenintramarginal.Totheextentthatthecrophectareyieldofthismarginalcropinthetenantfarmpulleddowntheaggregatedaverageyieldpercroparea,therelativelylowmarginalreturnsoftenantinputswouldbeconfirmed.
Ifweareabletoidentifythemarginalcropasdescribedabove,andifalargenumberoftenantfarmerssimultaneouslychosethesamecroptoaddintotheircroprotation,theaggregatedcrophectareyieldforthiscropwouldfall,regardlessofthefactthatthesamecropmighthavebeenintramarginalinsomefarms.Itfollowsthatwehavehereaproblemofcropidentification.Anycropmightindeedbeaddedatthemargin,andwhatinonetenantfarmwasthelastcroptobeaddedmightnotbethelastinanother.Weshallattempt,therefore,toidentifyaclassofcropswhosephysicalattributesaresuchthattheyarelikelytobeaddedatthemargin.Thatis,thephysicalattributesofplantingthemaresuchthattheirbeingaddedisconsistentwiththetheoryofchoiceundertheshareconstraint.Instillotherwords,thereexistsaclassofcropswhichhadnotbeenmonlyrotatedunderafreemarket,whereasunderthesharerestriction,petitionamongtenantssqueezedthemin.Thisclassofcropsweshallrefertoasmarginalcrops,inspiteofthefactthattheymightnotactuallybeaddedatthemarginonsomefarms.
Fromtheaboveitshouldbeclearthatundermoreintensivenonlandinputmitments,theyieldpercroparea(hectare)foranintramarginalcropislikelytorise,witharelativelysmallincreaseincroparea.Ontheotherhand,foramarginalcropthecrophectareyieldislikelytofall,witharelativelylargeincreaseincroparea.
[1].SinceTaiwanAgriculturalYearbookwillbecitedheavilyhereafter,itsmethodofdatacollectiondeservesattention.AccordingtoaletterfromYen-TienChang,CommissionerofTaiwanProvincialDepartmentofAgricultureandForestry,thefollowinginformationisprovided:
(1).Thethree-levelcrop-reportersareresponsibleforcollectingallbasicagriculturaldata.…Thereare720townshipreporterswhomakefieldsurveysandsubmitdatacollectedtohsien(county)government.Eachhsien(county)governmenthastwocrop-reportinginspectors,alltogether44ofthem,wholeadandinspectthetownshipreportersunderthem.Aftercheckingandprocessing,thecountyreporterssubmitthedatatotheProvincialDepartmentofAgricultureandForestry.
(2).Perhectareyieldiscalculatedbysample-cutting.Usuallyonesampleistakenfromevery100hectares.Surveysaremadefourtimesayeartorecordchanges.…
(3).Otherdata,suchascultivatedareaandpopulation,areobtainedfromtheProvincialLandBureauandtheProvincialDepartmentofCivilAffairsrespectively.
[2].Cultivatedlandisnotthesameasarableland.Thelatterareaisestimatedbythelandbureauaccordingtocertaingeologicalcriteria.Strictlyspeaking,alllandis"arable,"butwhetherornotitiseconomicallyworthwhiletocultivateissomethingelse.
[3].SeeSino-AmericanJointCommissiononRuralReconstruction,"JCRRAnnualReportsonLandReformintheRepublicofChina,"mimeographed(Taipei,1965),chap.8.
[4].Cropareaissometimescalledcroppingarea,crophectares,theareaofplantation,etc.SeeArthurW.Peterson,"AnEconomicStudyofLandUseinTaichungHsienandCity,1960,"mimeographed(Taichung:ResearchInstituteofAgriculturalEconomics,ChungHsingUniversity,1961);andNien-tsingLu,AnAnalysisofFarmFamilyEconomyofOwner-OperatorsundertheLand-to-the-TillerPrograminTaiwan(Taipei:ResearchDepartmentoftheLandBankofTaiwan,1965).
[5].Theone-halfcropofvegetablemaymeanthatonlyone-halfofthehectareoflandisbeingutilized,orthattheentirehectareisutilizedbutonlyhalfofthegrowingtimeiswithintheone-yearperiod.Thecropareavariesgreatlydependingonlandgradesandtheintensitiesofnonlandinputs.
[6].Sincehorticulturalcropsare"perennial,"theyarenotrotatedlike"annual"crops.Thesignificanceofthedecreaseintheirharvestedareawillbediscussedlater.
[7].Notethatwearespeakinghereofthecostofplantingonehectareofthesamecrop,notthecostperunitofoutput.Toconvertoneintotheother,aproductionfunctionisrequired.
B.OutputResponsesofIntramarginalCrops:Rice