Critical and Sensitive Periods of Health for Cognitive ...€¦ · Critical and Sensitive Periods...
Transcript of Critical and Sensitive Periods of Health for Cognitive ...€¦ · Critical and Sensitive Periods...
Modelandmethod:Themodelbeingestimatedisthefollowingproductionfunctionofskills:
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Criticalperiods(1)arewhenhealthinvestmenthasareturninoneperiodalone.Sensitiveperiods(2)arewhenthereisalargerreturninoneperiodthanothers(s≠t).
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Healthinthiscaseisendogenousbecauseofreversecausalityandparentschanginginvestmentbasedonunobservedfactors.Instrumentsincludebirthweight,mother’sheight,andheteroskedasiticty generatedinstruments(Lewbel [2012]).
CriticalandSensitivePeriodsofHealthforCognitiveAchievementinYoungPeruvianChildren
JohnCreamer,Heriot-WattUniversitySupervisors:CatherinePorter,MarkSchaffer
[email protected],@jcreamer_15
Introduction:Previousacademicresearchhasshowntheimportanceofearlyhealthonlaterlifeoutcomes.AlmondandCurrie(2011)statethatthefirst1,000daysoflifeisa“criticalperiod”ofhealthwherelaterlifeoutcomescanbeset.CunhaandHeckman(2007)introducetheideaofcriticalandsensitiveperiodstodescribehowinvestmenthasdifferentimpactsatdifferentperiodsoftime.
Thisstudyaimstocombinethesetheoriesbylookingatalifecourseanalysisofthefirstfiveyearsofachild’slife.ThedatacomesfromtheYoungLivesSurveyofPeru,focusingonacohortof2,000children.Itusesheightforagez-scoresatages1-2and4-5todetermineifhealthhasdifferentimpactsoncognitiveabilityatdifferentpointsintime.Instrumentsareusedtofindcausalestimates.Thesearecheckedbyweakidentificationrobustconfidenceintervals.
Conclusions:Therearethreekeyresultsfromthestudy:• Thereisnotevidenceofacausalrelationshipbetweenhealthinthefirstfiveyearsoflifeandcognitiveabilityacross
thefullsample.
• TheweakinstrumentrobustconfidenceintervalsshowthathealthisnotidentifiedbytheinstrumentsusedinthepastaswellastheLewbel heteroskedasticity generatedinstruments.Thisisimportantincomparisontothepastliterature.
• Thereisevidencehoweverthatthereisasensitiveperiodofdevelopmentforchildrenwhohavebeenstuntedatonepointintheirlives.Itispossiblethatinvestmentinhealthhasdiminishingmarginalreturnsoncestuntingisalleviated.
PleaseusetheQRcodetoreadthemostrecentversionof thepaper.ThedatausedinthispublicationcomefromYoungLives,a15-yearstudyof thechangingnatureofchildhood povertyinEthiopia, India,PeruandVietnam(www.younglives.org.uk) YoungLivesisfunded byUKaidfromtheDepartmentforInternationalDevelopment (DFID),withco-funding fromIrishAid.Theviewsexpressedherearethoseoftheauthor(s).TheyarenotnecessarilythoseofYoungLives,theUniversityofOxford,DFIDorotherfunders.
References:Almond,D.&Currie,J.HumanCapitalDevelopmentBeforeAgeFiveHandbookofLaborEconomics,2010,4(b),1315-1486Cunha,F.&Heckman,J.TheTechnologyofSkillFormationAmericanEconomicReviewPapersandProceedings,2007,97:2,31-47Lewbel,A.Usingheteroscedasticity toidentifyandestimatemismeasured andendogenousregressormodelsJournalofBusiness&EconomicStatistics,2012,30
Note:Goldpointdenotespointestimatesfromcol.3