chapter 8; popualtion grwoth and economic developm

Chapter8:PopulationgrowthandEconomicdevelopmentPopulation:somebasicconceptsFromeconomicdevelopmenttopopulationgrowthFrompopulationgrowthtoeconomicdevelopmentUntil2015,annualadditionstothepopulationareclosetothe90million.Inthischapter:howtheprocessofdevelopmenthasspurred(orretarded)populationgrowth.howpopulationgrowthinturnaffectseconomicdevelopment.Ourgoalswereasfollows:------todescribedemographictransition------toanalyzethesocialandeconomicfactorsthataffectfertilitydecisionsatthelevelofthehousehold.------totakenoteofbiasoflevelsoffertilitybetweenprivateoptimalandsociallyoptimal.-------tounderstandtheimpactofpopulationgrowthoneconomicdevelopment.8.1Population:somebasicconcepts一.BirthanddeathratesThesearenormallyexpressedasnumbersperthousandofthepopulationThepopulationgrowthrate:isthebirthrateminusthedeathrate.Table8.1providesuswithdataonbirthrates,deathrates,andpopulationgrowthratesforselectedlow-income,middle-income,andhigh-incomecountries.Appears:Atverylowlevelsofpercapitaincome,bothbirthanddeathratesarehigh.Thendeathsratesfall.Thepopulationgrowthratesseemtoriseandthenfalloverthecourseofdevelopment.二．AgedistributionsTheagedistributionofapopulationisgivenbyalistofproportionsofthatpopulationindifferentagegroups.Theagedistributionofdevelopingcountriesissignificantlyyoungerthanintheirdevelopedcounterparts.agedistributionaffectbirthanddeathsrates.1.AnaggregatebirthrateIstheoutcomeoftheagedistributioninacountry;theage–specificfertilityratesofwomeninthatcountry;thefractionofthepopulationindifferentagegroups.2.AnaggregatedeathrateIsacompositethatcomesfromage–specificdeathratesinaparticularcountry,aswellastheoverallagedistributioninthatcountry.age–specificfertilityrates:Istheaveragenumberofchildrenperyear-borntowomeninaparticularagegroup.Thetotalfertilityrate:Isfoundbyaddingupalltheage–specificfertilityratesoverdifferentagegroups:itisthetotalnumberofchildrenawomenisexpectedtohaveoverherlifetime.Hightotalfertilityratescontributetoahighrate;Thebirthratecanbesignificantlyhigh,evenifthetotalfertilityrateisnot.(inacountrywithayoungagedistribution).[alargerpercentageofthepopulationintheirreproductiveyears].Likewise,youngpopulationsarebiasedtowardlowdeathrates.Highratesofpopulationgrowth-------youngerpopulation------highbirthratesandlowdeathrates.------echoeffect----populationgrowthhigh.Conclusion:Fastgrowingsocietiesarealsoyoungsocieties.Thetotalfertilityratemaystillcausepopulationtoovershootadesiredtarget.(becauseofinertia)8.2Fromeconomicdevelopmenttopopulationgrowth一．Thedemographictransition1.Concept:Whichisadescriptionofthreephaseofpopulationgrowth.Anincreaseandthenadeclineintherateofpopulationgrowth;changingtheregimefromoneofhighbirthanddeathratestooneoflowbirthanddeathrates.Threephrase:Inphase1,bothbirthanddeathratesarehigh.Inphase2,deathratesfall,butbirthratesremainhigh.Inphase3,birthratesfollowthedeathrateonitsdownwardcourse.2.populationexplosionThebirthratesremainhighevenasdeathratesfall.Whydon’tbirthratesdeclinewithdeathrates?-------theforcesthatcauseddeathratestodeclinealsocausedeconomicproductivitytoincrease.Withroomforalargerpopulation,theurgencytobringdownthebirthratedissipated.----------inertia(fertilitychoicesmadebyhouseholds.)二．Theadjustmentofbirthrates1.Fertilitychoiceandmissingmarkets----Theanglethatweexploreinthissectionisthatoffspringaregenerallyasubstituteforvariousmissinginstitutionsandmarkets.Thatindividualswholackinsuranceandold-agesecurity,choosetoinvestinthefutureintheformofchildren.2.Theprobabilitythatachildwillgrowuptolookafteritsparents.Limitedpossibilitymayincreasefertilityasparentsattempttocompensateforthiscontingency.p:childgrowuptolookafteryou;q:acouplefindsacceptableasathresholdprobabilityofreceivingsupportfromatleastonechild.Supposeyouhavenchildren:(1-p)n:noneofthemlookafteryou.1-(1-p)nqp=1/2,q=9/10,-----thatnmustbeatleast4.q=95/100,-----5children.3.GenderbiasAfamilydesiressons,canincreasefertilityrates.4.HoardingversustargetingHoarding:childhavetobestockpiledinadvance,beforeweknowwhichamongthemwillprovidetherequisitesupport.Targeting:thedesirednumberofchildrencanbeattainedsequentially,thisstrategyiscalledtargeting.5.thecostsofchildrenDirectcosts:theyneedtobefed,clothed,keptingoodhealth,lookedafter,schooled.Indirectcosts(opportunitycosts.)Thataremeasuredbytheamountofincomeforegoneintheprocessofbringingupthechild.opportunitycostisproportionaltothegoingwageratemultipliedbythenumberofhoursspentinparenting.opportunitycostsislow,fertilityratestendtobehigh.Considertheeffectofincomeimprovementsonfertility.Figure8.1Incomeimprovementsandfertility0OthergoodschildrenabFa’b’gb’’e如果家庭收入提高，a’b’g点。如果孩子价格上升，ab’’e点。如果家庭收入和孩子净价格同时增加，预算线ab向下旋转，又向外移动到虚线cdh点。cdhF点为使家庭满足最大化的商品和孩子的组合点。6.Isfertilitytoohigh?Ifafamilychoosetohavealargenumberofchildren,thenwhyshouldsocialconsiderationsdictateanythingdifferent?Factorsthatcauseasystematicdeviationbetweendecisionsthatareprivatelyoptimal（fromthepointofviewofthefamily）anddecisionsthatareoptimalfrom