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Uri Simonsohn The Wharton School 1
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The paper in one slide: Jan 4 th 2007: Consumer Reports on carseats Jan 18 th : Retraction Unique opportunity: Do consumers continue using Jan 4 th info? Test on 6,000+ eBay auctions for carseats Main finding: Full return to baseline My interpretation: voluntarily ignored info. Alt explanations Information ‘depreciates’ Post-retraction buyers didn’t know Kind-of alternative: Sellers’ behavior 2
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Outline Background New information: release and retraction Auction data Main results Alternative specifications Conclusions 3
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Can people voluntarily ignore information they possess? Existing evidence: Debriefing paradigm Hindsight bias Anchoring Mock juries and inadmissible evidence 4
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Debriefing Paradigm Ross, Lepper & Colleageus (JPSP 1975;1980) Critique of false feedback in Psych Paradigm: Give false feedback on personality test Debrief: “feedback was false” Ask their beliefs …still influenced by retracted feedback 5
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Anchoring Subjects asked to make numerical estimate Length of Mississippi river WTP for keyboard. Asked first: is the amount larger or smaller than anchor. Final estimate is correlated with anchor. Even when anchor is roulette or SS# 6
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OPIM 690 Write down the last 2 digits of your SS#:__ Would you be willing to pay that amount for yearly access to NYTimes.com? What is the most you would pay? _____ 7
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Hindsight Bias People told some outcome Asked to estimate what those without information would predict. Finding: estimates are biased towards the to-be-ignored outcome. Next: results from Fischhoff (1975) 8
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Mock Juries & inadmissible evidence Dozens of studies Random assignment across “jurors” Control: baseline evidence T1: control + extra evidence T2: T1 + extra evidence is inadmissible. Decisions by T2 fall between control and T1. 10
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Outline Background New information: release and retraction Auction data Main results Alternative specifications Conclusions 12
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January 4 th, 2007 13 Corr( rank 2007,rank 2005) = -.08
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Retraction and empirical strategy Jan 18 th : Oops! Outsourced, 30 vs 38 vs 70 MPH Unique opportunity to study: 1) Causal effects of expert advice Contributions: ○ Individual level measures of WTP ○ Simple identification strategy (wrong info) Compared to -Discontinuities around discrete scores -Differences across sites -Timing 2) Ability of consumers to ignore retracted information. 14
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How would people learn of a new Consumer Rerports carseat rating? Important because: 1) Face validity of quick market reactions 2) Post-retraction awareness. 15
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From CR to consumers. CR in print Subscribers: slow ○ Library got it 01/11 ○ They claim: letter for retraction ○ Otherwise, not till May Newstands: slower ○ No retraction till May cr.org Comscore 100k users 15% of carseat buyers visit within 30 5% same day Not a direct source of info 16
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How about the media? 17
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Number of stories about “Consumer Reports” and “Carseats” sources: newsbank+lexisnexis 18 50+ Newspapers 600+ Stories
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Internet coverage Can’t do same search for web-coverage Can use web.archive.org to check specific sites. All major sites covered it 19
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In Sum CR info indirectly received via media Fast Retracted information remained available following retraction I’d argue: Post-retraction buyers probably read stories before being retracted. 20
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Outline Background New information: release and retraction Auction data Main results Alternative specifications Conclusions 21
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Why auctions Retailers don’t change prices often Few decision makers behind them Auctions: 1000s of DMs interacting Prices change continuously Aside: Unexploited side to eBay data: pulse on demand shocks. 22
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Auctions Data 6 months: 3 before & 3 after Many analyses focus on: ○ Before: 3 weeks ○ During: 2 weeks ○ After: 3 weeks Auctions: 6k Bids: 35k 23
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Descriptive statistics 25
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Annoyance: Shipping is only observed for sold items. Estimate OLS for sold items (w/shipping) Estimate Tobit for all (w.o./shipping) 26
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Outline or regression specifications Y: (tot.price i /Avg.Price i,k ) i:auction, k:carseat model Time variables (dummies): Primarily: before, during, after. Also: biweekly dummies (next slide) Also: 3-day-dummies Key predictor Primarily: ΔRanking Also: carseat-model-dummies e.g. Y=OLS(during*ΔRanking, after* ΔRanking, controls) 27
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First: bird’s eye view Estimate Y=OLS(biweekly*ΔRanking) 1 observation every 14 days. Plot point estimates 28 3.98 SD
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Next: more fine grained look Time: before, during, after 29
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Plotting time*dranking betas 31
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So far: just before-after How quick are the reactions? Y=OLS(3-day-dummies* Δranking) 32
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price=OLS(3-day dummies * Δrank) omitted cat.: two previous weeks 33
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How about non-winning bids? Camerer et al (1989) “Curse of Knowledge” Market forces reduce it Rational agents trade more Same here? Are non winning bidders ‘cursed’? Unit of observation: auction bid Quantile Regression 34
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Specification Bids are unit of observation. If more than one bid by same bidder, take highest only. Estimate quantile regressions of: bid $ = f(Time*ΔRanking) With quantiles at 20%,40%,60%,80%. 35
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Plotting the betas 37
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From ΔRanking to model-dummies Previous analyses: Impose Δ%price=b* ΔRanking Don’t allow for heterogeneity in effect Next: estimates by model. Plot avg(OLS,Tobit) 40
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Price=f(demand AND supply) 43
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Starting Price Number of paid features 45
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# of items for sale % New 46
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Summary of evidence Biweekly: biggest price drop in 6 months During vs. After: Market responded to information Ceased to once retracted 3-day: Market respond virtually immediately Quantile regressions Bidders across the full spectrum do so. Carseat dummies Every carseat (6/6) exhibits the pattern Supply: No evidence of changes in supply 48
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Interpretation Consumers successfully ignored information they possessed once it was retracted. 49
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Alternative Explanations 1) Knowledge depreciates …& coincides w/retraction But: 3-day graphs 2) Buyers never knew Retracted information still available online - Evenflo 50
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Why cursed in the lab but not here? Field, but not lab: credible instruction to ignore. Mock juries & substantive instructions Debriefing paradigm & credible instruction Should you really ignore info in ○ Hindsight Bias ○ Knowledge curse Field, but not lab: DM control information Dilution effect goes away when you can scratch irrelevant info Hindsight and anchoring attenuate when explicitly consider alternatives. 51
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Future research Run lab experiments explicitly manipulating variables that differ in vs. outside the lab. 52
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