Critical and Sensitive Periods of Health for Cognitive Achievement in Young Peruvian Children

CriticalandSensitivePeriodsofHealthforCognitiveAchievementinYoungPeruvianChildren

JohnCreamer,Heriot-WattUniversitySupervisors:CatherinePorter,MarkSchaffer

jfc1@hw.ac.uk,@jcreamer_15

Modelandmethod:Themodelbeingestimatedisthefollowingproductionfunctionofskills:

𝜃"# = 𝑓(𝐻"())), 𝐻"#+, , 𝑋"# , 𝐼#+(, 𝜇")

Criticalperiods(1)arewhenhealthinvestmenthasareturninoneperiodalone.Sensitiveperiods(2)arewhenthereisalargerreturninoneperiodthanothers(s≠t).

2345

264789≠ 0;

2345

264589= 0 1 ;

2345

264789>

2345

264589≠ 0(2)

Healthinthiscaseisendogenousbecauseofreversecausalityandparentschanginginvestmentbasedonunobservedfactors.Instrumentsincludebirthweight,mother’sheight,andheteroskedasiticty generatedinstruments(Lewbel [2012]).

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