《实验经济学》课程教学资源（参考文献）Testing for Altruism and SocialPressure in Charitable Giving

TESTING FOR ALTRUISM AND SOCIAL PRESSURE 11 hl(W-g)+av(g",G-)-s(g)+(1-h)[u(W-gm) +aw(0g,G_1-c(h). We characterize the optimal probability ofbeing at home.) in Ler Appendix)It is(weakly)increasing in altru ism:the more the giver cares about the charity (or the warm glow),the more likely she is to be at home.The exact pattern depends on the degree of social pressure (Figure I).In the case of no social pressure (S=0),sufficiently altruistic agents,a give ifh at home and actively seek to be at ho me (h* incre ng in the al- truism up to the corner solution h=1.Less altruistic agents, a s a(0),instead,do not plan to give.They are indifferent as to being at home or not,and hence do not alter the baseline probability ho. In the case of social pressure (S>0),agents with low altruism a (S) not give and avoid the fun raiser in ord not to pay the social pressure cost.More altruistic agents with a(S)<a ao(S)give a small amount but prefer to avoid the fund-raiser.Their giving is either entirely or partly due to social pressure.Agents with sufficiently high altruism,)care ugh about the charity that they seek the interaction with the fund raiser,de spite the fact that social pressure may distort their giving upward Opt-out.So far we have ass umed that it is costly to reduce the probability of being at home.We now allow agents to costlessly reduce the probability of being at home to 0,for example,via a Do-Not-Disturb check box on the flyer.Formally,c(0)=0 and c(h) as above for h0.5 Opting out does not affect giving g(a)(conditional on being at he (a)(con 10n ing at home)but only th probability of being at homeh(a).As characterized in Lemma 3 h*(a)remains the same as without the opt-out option if there is no social pressure and,hence,no reason to opt out.In the presence of social pressure,however,the agent opts out for low altruism,a since the interaction w ith the fund-raiser low wers utility. Forhigher altruism levels,instead,the agent derives posit 5.This formalization allows a costless s red ower

TESTING FOR ALTRUISM AND SOCIAL PRESSURE 11 max h∈[0,1] h [u (W − g∗) + av (g∗, G−i) − s (g∗)] + (1 − h)[u (W − g∗ m) +av (θg∗ m, G−i)] − c (h). We characterize the optimal probability of being at home, h∗(a, S), in Lemma 2 (see Appendix). It is (weakly) increasing in altru￾ism: the more the giver cares about the charity (or the warm glow), the more likely she is to be at home. The exact pattern depends on the degree of social pressure (Figure I). In the case of no social pressure (S = 0), sufficiently altruistic agents, a > a (0), give if at home and actively seek to be at home (h∗ > h0). The probability of being at home is increasing in the al￾truism up to the corner solution h = 1. Less altruistic agents, a ≤ a (0), instead, do not plan to give. They are indifferent as to being at home or not, and hence do not alter the baseline probability h0. In the case of social pressure (S > 0), agents with low altruism a ≤ a (S) do not give and avoid the fund-raiser in order not to pay the social pressure cost. More altruistic agents with a (S) < a ≤ a0 (S) give a small amount but prefer to avoid the fund-raiser. Their giving is either entirely or partly due to social pressure. Agents with sufficiently high altruism, a > a0 (S), care enough about the charity that they seek the interaction with the fund-raiser, despite the fact that social pressure may distort their giving upward. Opt-out. Sofarwehaveassumedthat it is costlytoreducethe probability of being at home. We now allow agents to costlessly reduce the probability of being at home to 0, for example, via a Do-Not-Disturbcheck box on the flyer. Formally, c (0)=0 andc (h) as above for h > 0.5 Opting out does not affect giving g∗(a) (conditional on being at home) or g∗ m (a) (conditional on not being at home) but only the probability of being at home h∗ (a). As characterized in Lemma 3, h∗ (a) remains thesameas without theopt-out optionif thereis no social pressure and, hence, noreason toopt out. In the presence of social pressure, however, the agent opts out for low altruism, a < a0 (S), since the interaction with the fund-raiser lowers utility. For higher altruism levels, instead, the agent derives positive 5. This formalization allows a costless reduction of h to 0 but not to other levels. This is not a restriction because agents who prefer to lower h below h0 (at a positive cost) will strictly prefer to lower h to 0 at no cost. by guest on September 20, 2012 http://qje.oxfordjournals.org/ Downloaded from

12 QUARTERLY JOURNAL OF ECONOMICS utility from giving.Hence,she does not opt out and the solution is the same as in Lemma 2. Opting out also allows us to distinguish social pressure from self-or other-signaling.In our model,checking the opt-out box has no cost to the agent.Under self-and other ci nalling.instead out is costly ce it signals avoida of giving If the cos is high,the agent will never opt out,and the opt-out treatment reduces to the simple flyer treatment. Testable Predictions.To complete the model,we assume that the population of agents is heterogeneous in a with c.d.f.F.We emphasize two special cases:(i)Altruism and No Social Pressure. that is.the standard assumption S=0.but a positive e probability of altruistic ndividuals with a cial p sure an Limited Altruism hat is,allowing f ure S>0,bu requiring 0 probability of altruistic individuals with a>ao(S). The following propositions outline testable predictions re- garding the key outcomes,home presence and giving.Our first oares the n robabilities of being at home in the ents w ut flyer,P(H)NF,with flyer,P(H)F,and with opt-out flyer P(Hoo. PROPOSITION 1.With Altruism and No Social Pressure,the probability P(H)is higher with flyer than without:P(H)= P(Hoo P(H) truis ver with flyer and I est with opt-out P(H)NE>P(HF≥ P(H)oo In the case of Altruism and No Social Pressure,the flyer increases home presence relative to the control group since some agents seek to meet the solicitor.The opt-out option has no differential effect since no one avoids the solicitor.Under Social and Limited Altruism, the oppo site is the fl eek to avoid ue. the solicitor.In thi case,the costless opt-out possibility lowers the presence at home further.In general,the probability of being at home is higher for the flyer group if the altruism force dominates the social pressure force,but the opt-out option always weakly lowers the presence at home 6.In case (ii),we also require F(ao(S))-F(a(S))>0to eliminate a trivial case to be of y)co ofor the in equality P()g 51

12 QUARTERLY JOURNAL OF ECONOMICS utility from giving. Hence, she does not opt out and the solution is the same as in Lemma 2. Opting out also allows us to distinguish social pressure from self- or other-signaling. In our model, checking the opt-out box has nocost tothe agent. Under self- andother-signalling, instead, opting out is costly since it signals avoidance of giving. If the cost is high, the agent will never opt out, and the opt-out treatment reduces to the simple flyer treatment. Testable Predictions. To complete the model, we assume that the population of agents is heterogeneous in a with c.d.f. F. We emphasize twospecial cases: (i) Altruism and No Social Pressure, that is, the standard assumption S = 0, but a positive probability of altruistic individuals with a > a (0); (ii) Social Pressure and Limited Altruism, that is, allowing for social pressure S > 0, but requiring 0 probability of altruistic individuals with a > a0 (S). 6 The following propositions outline testable predictions re￾garding the key outcomes, home presence and giving. Our first prediction compares the probabilities of being at home in the treatments without flyer, P (H)NF, with flyer, P (H)F, and with opt-out flyer P(H)OO. PROPOSITION 1. With Altruism and No Social Pressure, the probability P (H) is higher with flyer than without: P (H)F = P(H)OO > P (H)NF. With Social Pressure and Limited Al￾truism, P (H) is lower with flyer and lowest with opt-out: P (H)NF > P (H)F ≥ P (H)OO. In the case of Altruism and No Social Pressure, the flyer increases home presence relative to the control group since some agents seek to meet the solicitor. The opt-out option has no differential effect since no one avoids the solicitor. Under Social Pressure and Limited Altruism, the opposite is true: the flyer lowers home presence as agents seek toavoid the solicitor. In this case, the costless opt-out possibility lowers the presence at home further.7 In general, the probability of being at home is higher for the flyer group if the altruism force dominates the social pressure force, but the opt-out option always weakly lowers the presence at home. 6. In case (ii), we also require F(a0 (S) ) − F(a (S) ) > 0 to eliminate a trivial case. 7. A sufficient (not necessary) condition for the inequality P (H)F ≥ P (H)OO to be strict is a positive mass of households with a in the left neighbourhood of a0. by guest on September 20, 2012 http://qje.oxfordjournals.org/ Downloaded from

TESTING FOR ALTRUISM AND SOCIAL PRESSURE 13 The next roposition illustrates the impact of the different trea tments on the unconditional probability of in-person giving, P(G). PROPOSITION 2.With Altruism and No Social Pressure,the probability P(G)is higher with flyer than without:P(G)= p(CP(G)NF.With Social Pressure and Limited Al- with flyer and lowest with opt-out: P(G)NF>P(G)F≥P(G)oO Under Altruism and No Social Pressure,the flyer and opt-out treatments lead to the same probability of giving,since there is no reason to opt out in the absence of social pressure.The probability giving in these two flyer tre tme ents is high t flye ts see TT. K to S at hom ial p and Limited Altruism,instead,the probability of giving is lower with flyer and lowest with an opt-out flyer.In general,the net effect of a flyer depends on whether the giving is more due to real altruism(which works to increase giving)or to social pressure (which has the opp ite effect) The hird pre rds the probability of giving condi- tional on being at home,P(GH). PROPOSITION 3.The probability of giving conditional on being at home is higher with flyer than without:min(P(GH)r, P(GH)oo)P(GH)NF- Altruism and social pressure both lead to increases in the conditional giving probability with flyer:altruistic people are more likely to be at home,and nongivers sort away from home. Hence,conditionally on reaching an agent at home,giving is higher with than without flyer. 2 The next p oroposition focuses on gift size.We distinguish between large donations,defined asg>g,and small donations. g<. PROPOSITION 4.(i)The unconditional probability of a large do- nation,P(G),is higher with flyer than without:P(GHl)= P(G)P()(with strict inequality ifF(a)<1)(ii) The un nditional probability of a small donation,P(GLO),is identical simple flyer (P(GLO)g P(GLO)oo)if S>0 (and F(ao(S))- Fg(S))>0)

TESTING FOR ALTRUISM AND SOCIAL PRESSURE 13 The next proposition illustrates the impact of the different treatments on the unconditional probability of in-person giving, P (G). PROPOSITION 2. With Altruism and No Social Pressure, the probability P (G) is higher with flyer than without: P (G)F = P (G)OO > P (G)NF . With Social Pressure and Limited Al￾truism, P (G) is lower with flyer and lowest with opt-out: P (G)NF > P (G)F ≥ P (G)OO. Under Altruism andNoSocial Pressure, the flyer andopt-out treatments leadtothe same probability of giving, since there is no reason toopt out in the absence of social pressure. The probability of giving in these twoflyertreatments is higherthan without flyer because some agents seek to stay at home. Under Social Pressure and Limited Altruism, instead, the probability of giving is lower with flyer and lowest with an opt-out flyer. In general, the net effect of a flyer depends on whether the giving is more due to real altruism (which works to increase giving) or to social pressure (which has the opposite effect). The third prediction regards the probability of giving condi￾tional on being at home, P (G|H). PROPOSITION 3. The probability of giving conditional on being at home is higher with flyer than without: min (P(G|H)F, P(G|H)OO) ≥ P (G|H)NF . Altruism and social pressure both lead to increases in the conditional giving probability with flyer: altruistic people are more likely to be at home, and nongivers sort away from home. Hence, conditionally on reaching an agent at home, giving is higher with than without flyer. The next proposition focuses on gift size. We distinguish between large donations, defined as g > gs , and small donations, g ≤ gs . PROPOSITION 4. (i) The unconditional probability of a large do￾nation, P(GHI ), is higher with flyer than without: P(GHI)F = P(GHI)OO ≥ P(GHI )NF (with strict inequality if F(aˉ) < 1 ). (ii) The unconditional probability of a small donation, P(GLO), is identical under the simple flyer treatment and the flyer with opt out (P(GLO)F = P(GLO)OO) if S = 0 , but higher under the simple flyer (P(GLO)F > P(GLO)OO) if S > 0 (and F(a0 (S)) − F(a (S)) > 0). by guest on September 20, 2012 http://qje.oxfordjournals.org/ Downloaded from

14 QUARTERLY JOURNAL OF ECONOMICS A flyer (with or without opt-out option)increases large donations given that altruistic donors increase their probability of being at home.The impact of a flyer on small donations is less obvious since small donations can reflect moderate altruism or social pressure.A flyer with opt -out unambiguously lowers the pro y of small d onati the sorting ou of donors motivated by relative to a simple flyer The last proposition characterizes the probability of giving via mail. PROPOSITION 5.The unconditional probability of a donation while not at home P(Gm)satisfies 0=P(Gm)NF ,≤P(GmS P(Gm)oo. Without a flyer,giving via mail is zero because the giver is only informed about the fund-raiser if she is at home.A flyer informs the giver about the fund-raiser and,hence,she may give solon g as she is sufficiently altruistic.Giv e fy ng o nt as vith the simple flyer because some of the individuals who opt out because they would have given more than they wish in person give a smaller amount via mail. III.EXPERIMENTAL DESIGN Charities.The two charities in the fund-raising treatments are La Rabida Children's Hospital and the East Carolina Hazard Center(ECU).Although both charities are well-respected regional charities,we chose them so that most households in our sample would prefer one (La Rabida)to the other (ECU).To document thes in our 2008 5 survey tre atm we asked re spondents to rank five charities from 1 (least liked)to 5(most liked).The charity with the highest average rank is the La Rabida Children's Hospital (average rank 3.95)followed by Donate Life (rank 3.79),and the Seattle Children's Hospital (rank 3.47).At the bottom of the rank.below the Chicago Historical Society(rank 2.96),is the East Carolina Haz ard Center(rank 254).La Rabid appears to be highly liked both because it is an in-state charity well known to residents in the area around Chicago,and also 8 We ohtain simila an anon orha eded to gie to one of the five charities.(We foll Rabid e donat Out 255 charity,anc only 7choose t

14 QUARTERLY JOURNAL OF ECONOMICS A flyer (with or without opt-out option) increases large donations given that altruistic donors increase their probability of being at home. The impact of a flyer on small donations is less obvious since small donations can reflect moderate altruism or social pressure. A flyer with opt-out unambiguously lowers the probability of small donations relative toa simple flyer, given that it simplifies thesortingout of donors motivatedbysocial pressure. The last proposition characterizes the probability of giving via mail. PROPOSITION 5. The unconditional probability of a donation while not at home P(Gm) satisfies 0 = P(Gm)NF ≤ P(Gm)F ≤ P(Gm)OO. Without a flyer, giving via mail is zero because the giver is only informed about the fund-raiser if she is at home. A flyer informs the giver about the fund-raiser and, hence, she may give even if not at home, solong as she is sufficiently altruistic. Giving via mail is at least as high if the flyer offers opting out as with the simple flyer because some of the individuals who opt out because they would have given more than they wish in person give a smaller amount via mail. III. EXPERIMENTAL DESIGN Charities. The two charities in the fund-raising treatments are La Rabida Children’s Hospital and the East Carolina Hazard Center(ECU). Althoughbothcharities arewell-respectedregional charities, we chose them so that most households in our sample would prefer one (La Rabida) to the other (ECU). To document these preferences, in our 2008 survey treatments we asked re￾spondents to rank five charities from 1 (least liked) to 5 (most liked). Thecharitywiththehighest averagerankis theLa Rabida Children’s Hospital (average rank 3.95) followed by Donate Life (rank 3.79), and the Seattle Children’s Hospital (rank 3.47). At the bottom of the rank, belowthe ChicagoHistorical Society (rank 2.96), is the East Carolina HazardCenter (rank 2.54).8 La Rabida appears to be highly liked both because it is an in-state charity well known to residents in the area around Chicago, and also 8. We obtain similar results when we ask the respondents to allocate $1 that an anonymous sponsor has pledged to give toone of the five charities. (We followed up and delivered the donations.) Out of 255 respondents, 147 pledge the donation to the La Rabida charity, and only 7 choose the ECU charity. by guest on September 20, 2012 http://qje.oxfordjournals.org/ Downloaded from

TESTING FORALTRUISM AND SOCIAL PRESSURE 15 because it】 ovides health benefits to children;neither condition applies to ECU. Door-to-Door Fund-Raising.Our experiment uses a door-to- door campaign because it offers the easiest implementation of the des door g s(Landry et a200 nd previou d to quantify how much money they raise.To provide some evidence,our survey asked respondents to recall how many times in the past 12 months people have come to your door to raise money for a charity.We asked similarly phrased questions about giving via pho via ail,and through other chann as employer o friends.Of 44 responde ents who answered all of these questions. 76%stated that they had received at least one such visit.and 48 of respondents reported at least three such visits.This frequency is smaller than but comparable in magnitude to other solicitation forms:phone(86%received at least one call).mail(95%with at least one nailing),and other fo ct) We alsc Ld h muc res ndents gave to solicitors in total over the last 12 months.Of the respondents 40%reported donating to a door-to-door campaign,compared to 28%in response to phone solicitations,53%in response to mail solicitations,and76%in response to other solicitations. The av ge rep rted total doo donation in the 12 months ding $26 compared to phone,$1,012 by mail,and $2,063 by other means However, this estimate is very sensitive to a small number of individuals reporting large sums given (in two cases $50,000 and $60,000) which could be due to measurement error or self-aggrandizing 2 claims.If w the dor ation at $1,000,the are S26 by doo 66 by phone,$115 by mail,and 295 by othe means.Hence,door-to-door solicitations are quite common,at least in the area where the survey took place.and they raise a smaller,but not negligible,amounts. Logistics.We employed 92 solicitors and surveyors,mostly under raduate students at the University of chica wh paid50 per hour. A11 solicitors elicited tribu within at least two treatments,and most over multiple weekends,and similarly for surveyors.Each solicitor and surveyor's participa- tion in the study typically followed four steps:(1)an invita- tion to work as a paid volunteer for the research center,(2)

TESTING FOR ALTRUISM AND SOCIAL PRESSURE 15 because it provides health benefits to children; neither condition applies to ECU. Door-to-Door Fund-Raising. Our experiment uses a door-to￾door campaign because it offers the easiest implementation of the design. While door-to-door campaigns are common andpreviously studied in economics (Landry et al. 2006), it is hard to quantify how much money they raise. To provide some evidence, our survey asked respondents to recall how many times in the past 12 months people have come to your door to raise money for a charity. We asked similarly phrased questions about giving via phone, via mail, and through other channels, such as employer or friends. Of 144 respondents who answered all of these questions, 76% statedthat they hadreceivedat least one such visit, and48% of respondents reported at least three such visits. This frequency is smaller than but comparable in magnitude to other solicitation forms: phone (86% received at least one call), mail (95% with at least onemailing), andotherforms (83% withat least onecontact). We also asked how much the respondents gave to these solicitors in total over the last 12 months. Of the respondents, 40% reported donating to a door-to-door campaign, compared to 28% in response to phone solicitations, 53% in response to mail solicitations, and 76% in response to other solicitations. The average reported total door-to-door donation in the past 12 months (including nondonors) is $26, compared to $101 by phone, $1, 012 by mail, and $2, 063 by other means. However, this estimate is very sensitive to a small number of individuals reporting large sums given (in two cases $50, 000 and $60, 000) which could be due to measurement error or self-aggrandizing claims. If we cap the donations at $1, 000, the numbers are $26 by door-to-door, $66 by phone, $115 by mail, and $295 by other means. Hence, door-to-door solicitations are quite common, at least in the area where the survey took place, and they raise a smaller, but not negligible, amounts. Logistics. We employed 92 solicitors and surveyors, mostly undergraduate students at the University of Chicago, who were paid $9.50 per hour. All solicitors elicited contributions within at least two treatments, and most over multiple weekends, and similarly for surveyors. Each solicitor and surveyor’s participa￾tion in the study typically followed four steps: (1) an invita￾tion to work as a paid volunteer for the research center, (2) by guest on September 20, 2012 http://qje.oxfordjournals.org/ Downloaded from