"Landarea"inourtheoreticaldiscussionsmeanscultivatedland.WiththesmallportionofthecultivatedlandinTaiwanownedbythestateexcluded,allprivatelyownedlandusedforfarmingpurposesisincludedundercultivatedland,regardlessofhowmanycropsaregrowneachyearorwhethernocropisgrown.Intheanalysisoflandrentorlandareaassignedtoeachtenantunderasharecontract,thisspatial(physical)areaistherelevantmeasure.[2]DuringtheperiodunderstudyinTaiwan,partlybecausethecultivationofthelandatexternalmargins(arablebutnotprivatelyownedorcultivated)wouldyieldzeroorlowreturnsandmainlybecausetheexternalmarginswereownedbythestate,[3]theareaofcultivatedlandincreasedonlyslightly.Thisisshownintable3,column6.
Whereastheareaofcultivatedlandisquiteinflexibleovertime,thatisnotthecaseforcroparea.[4]Toillustrate,supposethatoveraone-yearperiod,onlyonecropofriceisgrownononehectareofcultivatedland;thenthecropareaisonehectare.If,overthesamephysicalareaforthesame(one-year)period,thefarmerrotatesonecropofrice,onecropofsweetpotatoes,andone-halfcropofvegetables,thenthecropareawillbecountedastwoandone-halfhectares.[5]Inshort,croparearepresentstherateofcroprotationoyeragivenareaofcultivatedlandperperiodoftime,measuredinhectaresofcropsactuallycultivated.Anincreaseincropareawithoutacorrespondingincreaseincultivatedlandmeansthatfarmingintensityhasincreasedthroughanincreaseintherateofcroprotation.
Asisseenintable3,using1948asthebaseyear,thecropareaofriceandmoncropsafterthesharerestrictionincreasedbyroughlythesamepercentage.Specialcropsincreasedmore,reachingapeakof21.5percentincreasein1950.Vegetablesincreasedthemostincroparea,reachingapeakof31.7percentincreasein1951;however,thecropareaforhorticulture(theareaharvested)decreased.[6]Thesevaryingchangesincropareasrepresentchangesinthefrequenciesofcropschosen.Asweshallseelater,theyconformtothepredictedpatternsofcropchoiceunderthesharerestriction.
TheDensityandRateofPlanting
Therearetwogeneralwaysbywhichtheincreaseoffarminginputsforafixedareaoflandcanbemitted.Onewayistoholdthecropareaunchanged,buttoincreasetheyieldpercropbyusingbetterseeds,fertilizers,andpesticides,improvingirrigation,repairingfields,andperhapsplantingtheplantsclosertoeachother.Thismethodweshallcallincreasingthedensityofplanting.Anotherwaytoincreasetheoutputonagivenareaoflandistospeeduptherateofcroprotation,thusincreasingthecroparea.Thiscanbedonebyplantingadditionalcropsduringanotherwiseidleseason,by"shortening"thegrowingtimerequiredforeachcropbyrelaying,interplanting,orearlierharvesting.Givenanadditionalamountoftenantinputstobemittedunderthesharerestriction,aportionoftheincrementalinputswillbeallocatedtothedensityofplantingandaportionwillbeallocatedtotherateofplanting.
Anincreaseinthedensityofplantingimpliesahighercostofplantingforthesamecroparea.Providedthatthemarginalproductoftenantinputisabovezero,theyieldpercropareawillrise.Itisalsoclearthatanincreaseintherateofplanting,withacorrespondingincreaseincroparea,impliesahigherplantingcostpercropareaforthesamecrop.Atleasttworeasonscanbeoffered.Thefirstisthetechnicalproblemoffasterrotation;forexample,itcostsmoretorelayorinterplant(tosqueezein)anextracropthantoplantthesamecropwithoutrelaying.Andthesecond,whichperhapsincludesthefirst,isthathastemakesahighercost.[7]Unlikeincreasingdensity,wheretheyieldpercropareawillrise,theincreaseinplantingratemayleadtoaloweryieldpercroparea.
IntramarginalandMarginalCrops
Thecriticaltestoftheimplicationthatmarginalproductsoftenantinputsdecreaseistheresponseofthemarginalcrops.Imagineatenantfarmwhichhadgrownonecropofriceperyearbeforethesharerestriction,andsupposethatthisricecropcontinuedtobegrownafterwardsbutwithhigherdensityofplanting.Thericeyieldpercropareawouldrise.Here,wecallricetheintramarginalcropbecauseitwasgrownonthefarmbeforethesharerestrictionaswellasafter.Underthesharerestriction,thedensityofplantingofthisricecropwouldbeincreased,andthecorrespondingriseincrophectareyieldimpliesthatboththeaverageandmarginalproductoflandincreased.Thisincreasedyieldpercropareaisalsoconsistentwithdecreasingmarginalreturnstotenantinputs.Withoutincrementalcostdata,however,confirmationofourconclusion,thatthemarginalcostoftenantinputsisnecessarilygreaterthantheassociatedmarginalproduct,isnotpossible.
Suppose,onanotherowner-cultivatedfarm,ricehadalsobeenanintramarginalcrop.Underthesharerestriction,thereallocationofnonlandresourcesfromownerfarmstotenantfarmswouldtendtoleadtoadecreaseinthedensityofplantingonthisownerfarm.Thecropareayieldforriceontheownerfarmwoulddecrease.Intheaggregateddataavailable,theaveragecroparea(hectare)yieldforricemightriseorfall.Theaggregatedaveragewouldriseif(1)resourcesweredrawnintoagriculturetotheextentthattheincreaseinriceyieldonthetenantfarmoutweighedthedecreaseinyieldontheownerfarm,or(2)ricewasdominantlytheintramarginalcropoftenantfarms.