TheWelfareEffectsofSocialMediaHuntAllcott,LucaBraghieri,SarahEichmeyer,andMatthewGentzkow*January27,2019AbstractTheriseofsocialmediahasprovokedbothoptimismaboutpotentialsocietalbenefitsandconcernaboutharmssuchasaddiction,depression,andpoliticalpolarization.WepresentarandomizedevaluationofthewelfareeffectsofFacebook,focusingonUSusersintherun-uptothe2018midtermelection.Wemeasuredthewillingness-to-acceptof2,844FacebookuserstodeactivatetheirFacebookaccountsforfourweeks,thenrandomlyassignedasubsettoactuallydosoinawaythatweverified.Usingasuiteofoutcomesfrombothsurveysanddirectmeasurement,weshowthatFacebookdeactivation(i)reducedonlineactivity,includingothersocialmedia,whileincreasingofflineactivitiessuchaswatchingTValoneandsocializingwithfamilyandfriends;(ii)reducedbothfactualnewsknowledgeandpoliticalpolarization;(iii)increasedsubject