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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 2025. I also include the description from the original paper below.

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; 2026). Several people have asked me if I have an update. In this document I update all figures and numbers to show the details for 2025. I also include the description from the 2019 paper below.

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 2025. 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; 2026).

John A List

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List Experiments are widely used across the social sciences to measure sensitive attitudes and behaviors, yet no prior study has validated their estimates against an incentive-compatible behavioral measure. I conduct a field experiment with 400 subjects at a sports card show, combining List Experiment treatments for willingness to pay, one for wolf reintroduction in Yellowstone Park, one for a graded sports card, with a Vickrey second-price auction that provides a real-money benchmark. The List Experiment estimates 26% would pay $50 for the card, compared to 22% who bid at least that amount in the auction; this difference is not statistically significant. These results provide the first criterion validity test of a List Experiment and suggest the method holds promise as a parsimonious alternative to conventional stated preference approaches in settings where survey space constraints preclude standard bias-mitigation interventions.

John A List

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Many ideas show remarkable returns in small-scale trials but often disappoint when scaled to broader populations and contexts. Using early childhood investment as a case study, this study develops a dynamic human capital formation model that integrates complementary skill investment with "Option C thinking" on scaling challenges. The model is stylized in the Chicago tradition: micro-founded with optimizing agents, dynamic skill production, and a policymaker evaluating scaling decisions. It formalizes how naive extrapolation from pilot studies systematically overestimates policy efficacy by ignoring "voltage drops," declining treatment effects due to unrepresentativeness at scale. The model demonstrates that optimal scaling policy requires mechanism-based design that anticipates these failures through backward induction from implementation realities. The scientific insights from a set of recent studies provide valuable perspectives on the model.

Lancelot H de Frahan, Joseph Goodman, Justin Holz, John A List, Evan McKay, Niall McMenamin, Magne Mogstad, Sally Sadoff, Hal Sider

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We leverage Becker's time allocation theory to examine consumer demand and market competition for time-intensive goods. The Beckerian model predicts higher diversion ratios for goods with substantial time shares and those with high time costs relative to monetary prices. Applying this model to data from two field experiments, we analyze demand for Facebook and Instagram, focusing on substitution patterns across online activities and offline time use. Our findings indicate that users exhibit low elasticity to ad load, the primary user cost, and that time shares and time costs significantly influence diversion ratios. We explore the implications for user costs and benefits on these platforms and assess the potential impact of a Federal Trade Commission-proposed de-merger of Facebook and Instagram.

Caroline Gaudreau, Dani Levine, John A List, Dana L Suskind

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Research shows responsive caregiving enhances children's brain development, with parental knowledge predicting positive behaviors and outcomes. However, knowledge varies widely across educational levels, highlighting the need for targeted interventions. Despite evidence that this knowledge can be improved, no comprehensive metric exists for efficient assessment. We introduce SPEAK (Survey of Parent/Provider Expectations and Knowledge), a computer adaptive tool grounded in item-response theory that we created, to address this gap by measuring parental and educator knowledge across development domains with precision and speed. This paper details SPEAK's development, including domain construction, cognitive interviewing, expert review, psychometric calibration, and validity evidence. SPEAK offers a flexible, scalable solution for clinical, educational, research, and policy settings. By identifying knowledge gaps, it enables tailored interventions, supports professional development, and informs policy, ultimately improving parent-child interactions and child outcomes. Our tool bridges critical gaps in assessing child development knowledge, advancing research and cross sector collaboration to promote early childhood development worldwide.

Christopher Cotton, Brent R Hickman, John A List, Joseph Price, Sutanuka Roy

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Using field-experimental data (study-time tracking and randomized incentives), we identify a structural model of learning. Student effort is influenced by external costs/benefits and unobserved heterogeneity: motivation (willingness to study) and productivity (conversion rate of time into skill). We estimate academic labor-supply elasticities and skill technology. Productivity and motivation are uncorrelated. Low productivity, not low motivation, is the stronger predictor of academic struggles. School quality augments productivity and accelerates skill production. We find that dynamic skill complementarities arise mainly from children's aging and from a feedback loop between investment activity and productivity, rather than from carrying forward past skill stocks.

Uditi Karna, John A List, Andrew Simon, Haruka Uchida

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Parents are crucial to children's educational success, but the role of parental education in fostering academic excellence remains underexplored. Using longitudinal administrative data covering all North Carolina public school students, we document five facts about first generation excellence gaps. We find large excellence gaps emerge by 3rd grade across all demographics and persist through high school. Yet, socioeconomic status and school quality explain only one-third of the gaps. The overarching facts reveal that excellence gaps reflect deeper challenges rooted in parental human capital that manifest early and compound over time, rather than merely consequences of socioeconomic disadvantage or school quality differences.

Guglielmo Briscese, John A List, Sabrina Liu

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With higher education costs consistently outpacing inflation and public funding declining, college affordability has become a critical barrier to economic mobility for middle- and low-income families. While College Savings Accounts (CSAs), or 529 plans, offer tax advantaged vehicles for college savings, their adoption patterns and educational impacts remain poorly understood. Using comprehensive administrative data from over 900,000 Illinois 529 accounts (2000-2023) linked to educational outcomes, plus complementary surveys of account owners and parents, we provide the first large-scale analysis of CSA participation and effectiveness. We find that while CSA adoption has expanded to every ZIP code in Illinois, participation remains concentrated among higher-income, more educated families. Financial literacy emerges as a key barrier: 61% of parents who could save enough to cover half of future college costs still perceive their potential savings as meaningless. Among participants, higher savings are strongly correlated with better educational outcomes, including four-year college enrollment, attendance at selective institutions, and the pursuit of post-graduate degrees. These findings suggest that targeted interventions addressing financial literacy gaps and misperceptions about modest savings could significantly expand CSA effectiveness as a tool for educational equity. Beyond state-level 529 program optimization, our findings suggest several promising avenues for federal policy coordination and institutional innovation.

(JPE-Micro) Journal of Political Economy: Microeconomics

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We are excited to announce a special issue dedicated to the “Science of Scaling” in the Journal of Political Economy: Microeconomics. This special issue aims to advance rigorous, interdisciplinary research on scaling as a scientific endeavor, building on the growing recognition that scaling extends beyond mere policy implementation to encompass fundamental questions about generalizability, benefit-cost analysis, and real-world application of empirical findings.

Faith Fatchen, John A. List, Francesca Pagnotta

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In recent years, field experiments have reshaped policy worldwide, but scaling ideas remains a thorny challenge. Perhaps the most important issue facing policymakers today is deciding which ideas to scale. One approach to attenuate this information problem is to augment traditional A/B experimental designs to address questions of scalability from the beginning. List 2024 denotes this approach as “Option C” thinking. Using early education as a case study, we show how AI can overcome a critical barrier in Option C thinking – generating viable options for scaling experimentation. By integrating AI-driven insights, this approach strengthens the link between controlled trials and large-scale implementation, ensuring the production of policy-based evidence for effective decision-making.

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.