Papers - Recent

Jesper Akesson, Robert Hahn, Robert D Metcalfe, Manuel Monti-Nussbaum

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Although fake online customer reviews have become prevalent on platforms such as Amazon, Google, and Facebook, little is known about how these reviews influence consumer behavior. This paper provides the first experimental estimates of the effects of fake reviews on individual demand and welfare. We conduct an incentive-compatible online experiment with a nationally representative sample of respondents from the United Kingdom. Consumers are asked to choose a product category, browse a platform resembling Amazon, and select one of five equally priced products. One of the products is of inferior quality, one is of superior quality, and three are of average quality. We randomly allocate participants to variants of the platform: five treatment groups see positive fake reviews for an inferior product, and the control group does not see fake reviews. Moreover, some participants are randomly selected to receive an educational intervention that aims to mitigate the potential effects of fake reviews. Our analysis of the experimental data yields four findings. First, fake reviews make consumers more likely to choose lower-quality products. Second, we estimate that welfare losses from such reviews may be important - on the order of .12 dollars for each dollar spent in the setting we study. Third, we find that fake reviews have heterogeneous effects. For example, the effect of fake reviews is smaller for those who do not trust customer reviews. Fake reviews also have larger effects on those who shop online more frequently. Fourth, we show that the educational intervention reduces the adverse welfare impact of fake reviews by 44%.

Jesper Akesson, Robert Hahn, Rajat Kochhar, Robert D Metcalfe

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Water suppliers are showing greater interest in using different mechanisms to promote conservation. One such mechanism is conducting home water audits, which involves assessing water use and providing tailored suggestions for conserving water for residential customers. Yet, very little is known about the economic impacts of these water audits. This paper helps fill this gap by implementing a natural field experiment in the United Kingdom. The experiment randomly allocates 45,000 water customers to a control group or to treatment groups that receive different behavioral encouragements to take-up an online water audit. Our analysis yields three main findings. First, encouraging subjects to participate in an audit with financial incentives reduces household consumption by about 17 percent over two months. Furthermore, we find that the size of the financial incentive used to encourage conservation matters for take-up, but not conservation. Second, although there are substantial improvements in water conservation for some interventions, they do not appear to yield net benefits of more than 1 pound per person under various sensitivity analyses. We also implement a marginal value of public funds approach that considers benefits and costs and reach a similar conclusion. Third, we find that targeting high users could double the effectiveness of the financial incentive interventions.

Robert D Metcalfe, Sefi Roth

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Exposure to ambient air pollution has been shown to be detrimental to human health and productivity, and has motivated many policies to reduce such pollution. However, given that humans spend 90% of their time indoors, it is important to understand the degree of exposure to Indoor Air Pollution (IAP), and, if high, ways to reduce it. We design and implement a field experiment in London that monitors households' IAP and then randomly reveals their IAP in real-time. At baseline, we find that IAP is worse than ambient air pollution when residents are at home and that for 38% of the time, IAP is above World Health Organization standards. Additionally, we observe a large household income-IAP gradient, larger than the income-ambient pollution gradient, highlighting large income disparities in IAP exposure. During our field experiment, we find that the randomized revelation reduces IAP by 17% (1.9 ug/m3) overall and 34% (5 ug/m3) during occupancy time. We show that the mechanism is households using more natural ventilation as a result of the feedback (i.e., opening up doors and windows). Finally, in terms of welfare, we find that: (i) households have a willingness to pay of 4.8 pounds (6 dollars) for every 1 ug/m3 reduction in indoor PM2.5; (ii) households have a higher willingness to pay for mitigation than for full information; (iii) households have a price elasticity of IAP monitor demand around -0.75; and (iv) a 1 pound subsidy for an IAP monitor or an air purifier has an infinite marginal value of public funds, i.e., a Pareto improvement.

Daryl Fairweather, Matthew E. Kahn, Robert D Metcalfe, Sebastian Sandoval-Olascoaga

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Climate change presents new risks for property in the United States. Due to the high cost and sometimes unavailability of location-specific property risk data, home buyers can greatly benefit from acquiring knowledge about these risks. To explore this, a large-scale nationwide natural field experiment was conducted through Redfin to estimate the causal impact of providing home-specific flood risk information on the behavior of home buyers in terms of their search, bidding, and purchasing decisions. Redfin randomly assigned 17.5 million users to receive information detailing the flood risk associated with the properties they searched for on the platform. Our analysis reveals several key findings: (1) the flood risk information influences every stage of the house buying process, including the initial search, bidding activities, and final purchase; (2) individuals are willing to make trade-offs concerning property amenities in order to own a property with a lower flood risk; (3) the impact of the flood risk information on behavior is more pronounced for users conducting searches in high flood risk areas, but does not differ significantly between buyers in Republican and Democrat Counties; and (4) the information resulted in changes to property prices and altered the market's hedonic equilibrium, providing a new finding that climate adaptation can be forward-thinking and proactive.

John A. List

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A discussion on how ChatGPT can be used to help design experiments that can be scaled.

John A. List

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In 2019, I put together a summary of data from my field experiments website that pertained to natural field experiments (Harrison and List, 2004). Several people have asked me for updates. In this document I update all figures and numbers to show the details for 2024. I also include the description from the original paper below.

Anouk L. Schippers, Adriaan R Soetevent

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Informal peer-to-peer services to share or barter goods often succumb to free riding behavior because they lack the tools to enforce compliance and reciprocity. We collect unique quantitative data on a form of unregulated peer-to-peer in-kind exchange that appears internationally viable: the free exchange of books via privately owned public bookcases, also known as little free libraries. Other than previously studied honor-based exchanges, little free libraries use a non-monetary one-to-one book exchange rate. We find surprisingly limited free riding in this market. Users return 9 books for every 10 taken. An incentivized survey points to strong social norms and preferences for cooperation among owners and users as key behavioral primitives that can explain the observed high and stable level of reciprocal exchange.

Toke R. Fosgaard, Adriaan R Soetevent

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Given the replacement of cash with cell phone payments, people who are asked to donate to charity can easily promise a donation but delay the transfer until a later date. This may be a way to get out of the ask-situation with a positive image while maintaining the flexibility not to donate. This study explores whether charities can make people keep their promises by making such promises more explicit and more formal. In a door-to-door fund-raising field experiment, we vary the strength of the promise that donors make. Besides a control group where people can promise to donate, we apply two treatment groups. In the first treatment, donors are asked to verbally pledge a precise amount. In a second treatment, this amount is in addition put on paper with the solicitor's signature added. Both treatments are aimed at making it morally more expensive not to keep promises. Our results show that: (1) the majority of people do not follow through on their promise to donate; (2) donors who pledge an explicit amount more often keep their promise. The more formal the commitment, the closer the amount donated is to the amount promised; (3) many participants refuse to pledge a donation amount when asked, and those who refuse donate significantly less.

Gert-Jan Romensen, Adriaan R Soetevent

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An often-voiced concern with relative performance feedback is that it may not improve workplace productivity if workers become demotivated and see no way to improve. Targeting feedback at specific productivity measures over which workers have direct control may in such cases prevent demotivation and focus attention. Does targeting improve worker productivity? We partner with a large bus company and experimentally vary the nature and number of peer-comparison messages which 409 bus drivers receive in their monthly feedback report. Messages are targeted at concrete driving behaviors and aimed at improving comfort and fuel efficiency. Using over 800,000 trip-level observations, we find that these targeted peer-comparison messages do not improve aggregate (fuel economy) or disaggregate measures (such as acceleration) of driving behavior. Further analyses also reveal no temporal or heterogeneous effects of the targeted messages.

Sander Onderstal, Arthur J.H.C. Schram, Adriaan R Soetevent

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In a door-to-door fundraising field experiment, we study the impact of fundraising mechanisms on charitable giving. We approached about 4500 households, each participating in an all-pay auction, a lottery, a non-anonymous voluntary contribution mechanism (VCM), or an anonymous VCM. In contrast to the VCMs, households in the all-pay auction and the lottery competed for a prize. Although the all-pay auction is the superior fundraising mechanism both in theory and in the laboratory, it did not raise the highest revenue per household in the field and even raised significantly less than the anonymous VCM. Our experiment reveals that this can be attributed to substantially lower participation in the all-pay auction than in the other mechanisms while the average donation for those who contribute is only slightly (and statistically insignificantly) higher. We explore various explanations for this lower participation and favor one that argues that competition in the all-pay mechanism crowds out intrinsic motivations to contribute.

Adriaan R Soetevent

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This paper examines the impact of payment choice on charitable giving with a door-to-door fund-raising field experiment. Respondents can donate cash only, use debit only, or have both options. Cash donations have lower visibility vis-a-vis solicitors than debit card donations. When debit replaces cash, participation drops by 87 percent. Conditional on participation, donors in the Debit-only treatment give more than donors in Cash-only. In Cash&Debit, almost all donors prefer cash; participation decreases compared to Cash-only. Physical attractiveness of both female and male solicitors increases contributions. Solicitor self-confidence has a negative impact.

Michael G. Cuna, Lenka Fiala, Min Sok Lee, John A. List, Sutanuka Roy

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This study examines how mothers' risk and ambiguity preferences affect early childhood investments and outcomes by assessing over 6,000 mothers in Rajasthan, India. Results show that more risk and ambiguity averse mothers make greater investments in their children's nutrition between ages 0-6. These investments correlate with superior cognitive and non-cognitive skills in children, even after controlling for socioeconomic factors. Notably, higher maternal risk and ambiguity aversion can mitigate negative impacts of socioeconomic disadvantages (maternal illiteracy, belonging to historically discriminated groups, limited media access) on all measures of early-life skills, highlighting the importance of understanding preferences in addressing inequities.

John A. List

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Contingent valuation is a widely used method for estimating the value of nonmarket commodities. Yet, a persistent issue is whether responses to Contingent Valuation Method (CVM) questions accurately reflect true values. Recent studies indicate that hypothetical bias is a significant factor that creates a gap between intentions and actions. I use a novel approach within non-market valuation - a List Experiment in the field - to test whether it can attenuate the hypothetical bias observed within CVM surveys. Using data from 400 subjects in a field experiment, I find initial promising results.

John A. List

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In 2019 I put together a summary of data from my field experiments website that pertained to framed field experiments (see List 2024; 2025). Several people have asked me if I have an update. In this document I update all figures and numbers to show the details for 2024. I also include the description from the 2019 paper below.

Uditi Karna, Min Sok Lee, John A. List, Andrew Simon, Haruka Uchida

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Educational disparities remain a key contributor to increasing social and wealth inequalities. To address this, researchers and policymakers have focused on average differences between racial groups or differences among students who are falling behind. This focus potentially leads to educational triage, diverting resources away from high-achieving students, including those from racial minorities. Here we focus on the "racial excellence gap" - the difference in the likelihood that students from racial minorities (Black and Hispanic) reach the highest levels of academic achievement compared with their non-minority (white and Asian) peers. There is a shortage of evidence that systematically measures the magnitude of the excellence gap and how it evolves. Using longitudinal, statewide, administrative data, we document eight facts regarding the excellence gap from third grade (typically ages 8-9) to high school (typically ages 14-18), link the stability of excellence gaps and student backgrounds, and assess the efficacy of public policies. We show that excellence gaps in maths and reading are evident by the third grade and grow slightly over time, especially for female students. About one third of the gap is explained by a student's socioeconomic status, and about one tenth is explained by the school environment. Top-achieving racial minority students are also less likely to persist in excellence as they progress through school. Moreover, state accountability policies that direct additional resources to reduce non-race-based inequality had minimal effects on the racial excellence gaps. Documenting these patterns is an important step towards eliminating excellence gaps and removing the "racial glass ceiling".

John A. List, Haruka Uchida

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Excellence gaps - disparities in advanced academic achievement - between racial groups appear by age 8 or 9 and persist throughout secondary school in the United States. About one-third of the gap is due to socio-economic status and one-tenth to school factors, indicating that policies should address both educational and local environments.

Michael G. Cuna, Musharraf Cyan, M. Taha Kasim, John A. List, Michael K Price

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From newborns to the elderly, exposure to violence and conflict has been found to have deleterious effects. In this study, we explore a unique type of violence: exposure to the Taliban. Pairing a field experiment with a field survey among citizens in Khyber Pakhtunkhwa (KP), Pakistan, we examine how exposure to violence affects general trust, subjective well-being, and confidence in institutions. In our field experiment, we observe that exposure to conflict significantly alters the relative valuation of monetary rewards for oneself compared to those for a comparable peer. Specifically, individuals subjected to violence demonstrate a marked tendency to prioritize their own financial gain over that of a similar other. In the survey, we find that exposure to violence is associated with reduced general trust, trust in informal institutions, and subjective well-being. Interestingly, being exposed to violence increases trust in formal institutions. Our combined results highlight that the interplay between violence and trust dynamics is complex and highly consequential. In turn, the policy implications highlight the need for a multifaceted strategy to support individuals and communities affected by violence, ensuring both immediate relief and long-term resilience.

John A. List

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The traditional approach in experimental economics is to use a between-subject design: the analyst places each unit in treatment or control simultaneously and recovers outcome differences via differencing conditional expectations. Within-subject designs represent a significant departure from this method, as the same unit is observed in both treatment and control conditions sequentially. While some might consider the design choice straightforward (always opt for a between-subject design), I contend that researchers should meticulously weigh the advantages and disadvantages of each design. In doing so, I propose a categorization for within-subject designs based on the plausibility of recovering an internally valid estimate. In one instance, which I denote as stealth designs, the analyst should unequivocally choose a within-subject design rather than a between-subject design.

John A. List

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In 2019, I put together a summary of data from my field experiments website that pertained to artefactual field experiments. Several people have asked me if I have an update. In this document I update all figures and numbers to show the details for the year 2024. I also include the description from the 2019 paper below. The definition of artefactual field experiments comes originally from Harrison and List (2004) and is advanced in List (2006; 2024, 2025).

Majid Ahmadi, Gwen-Jiro Clochard, Jeff Lachman, John A. List

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When multiple forces potentially underlie discriminatory behavior, pinning down the precise sources becomes a challenge, making proposed policy solutions speculative. This study introduces an empirical approach, tightly linked to theory, to dissect two specific channels of discrimination: customer bias and managerial bias. To illustrate our framework, we integrate proprietary data with several publicly available datasets to uncover channels of discrimination within the Major League Baseball draft. Our analysis reveals that customer preferences significantly influence the drafting of players at the top end of the draft - those likely to gain immediate public attention and eventually play for the club. Conversely, we observe managerial homophily in the latter parts of the draft, where players who attract little attention and have minimal chances of playing for the club are selected. The observed preferential bias at both ends of the draft incurs a substantial opportunity cost. However, bias at the top end unduly affects competitiveness. Our findings provide significant implications for future research on measuring discrimination and addressing the challenge of multiple channels.