regression discontinuity and pipeline methods

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1、7.RegressionDiscontinuityandPipelineMethodsSummaryInanonexperimentalsetting,programeligibilityrulescansometimesbeusedasinstrumentsforexogenouslyidentifyingparticipantsandnonparticipants.Toestablishcomparability,onecanuseparticipantsandnonparticipantswithinacertainneigh-borhoodoftheeligibilityt

2、hresholdastherelevantsampleforestimatingthetreat-mentimpact.Knownasregressiondiscontinuity(RD),thismethodallowsobservedaswellasunobservedheterogeneitytobeaccountedfor.Althoughthecutofforeligibilitythresholdcanbedefinednonparametrically,thecutoffhasinpracticetraditionallybeendefinedthroughaninstr

3、ument.ConcernswiththeRDapproachincludethepossibilitythateligibilityruleswillnotbeadheredtoconsistently,aswellasthepotentialforeligibilityrulestochangeovertime.Robustnesscheckscanbeconductedtoexaminethevalidityofthediscontinuitydesign,includingsuddenchangesinothercontrolvariablesatthecutoffpoin

4、t.Examiningthepatterninthevariabledeterminingeligibilitycanalsobeuseful—whether,forexample,theaverageoutcomeexhibitsjumpsatvaluesofthevariableotherthantheeligibilitycutoff—aswellasanydiscontinuitiesintheconditionaldensityofthisvariable.Pipelinecomparisonsexploitvariationinthetimingofprogramimp

5、lementation,usingasacomparisongroupeligibleparticipantswhohavenotyetreceivedthepro-gram.Oneadditionalempiricalstrategyconsideredbyprogramevaluatorsistoexploitdataonprogramexpansionalongagivenroute(forexample,aninfrastructureprojectsuchaswater,transport,orcommunicationnetworks)tocompareoutcomes

6、foreli-gibleparticipantsatdifferentsidesoftheprojectboundaryastheprogramisphasedin.ThismethodinvolvesacombinationofpipelineandRDapproachesthatcouldyieldinterestingcomparisonsovertime.LearningObjectivesAftercompletingthischapter,thereaderwillbeabletodiscuss■RDasamethodthataccountsforpotentialse

7、lectionorparticipationonobservedandunobservedcharacteristics■Robustnesscheckstoensurethatthediscontinuitydesignandeligibilitycutoffsarevalid103HandbookonImpactEvaluation■Theidentificationstrategyofpipelinecomparisons■WaystocombinetheRDap