Knowledge that Transforms

Is more novel research always desirable? We develop a model in which knowledge shapes society's policies and guides the search for discoveries. Researchers select a question and how intensely to study it. The novelty of a question determines both the value and difficulty of discovering its answer. We show that the benefits of discoveries are nonmonotone in novelty. Knowledge expands endogenously step-by-step over time. Through a dynamic externality, moonshots -- research on questions more novel than what is myopically optimal -- can improve the evolution of knowledge. Moonshots induce research cycles in which subsequent researchers connect the moonshot to previous knowledge.

Using randomized control trials (RCTs) applied over time in different countries, we study whether the economic environment affects how agents learn from new information. We show that as inflation rose in advanced economies, both households and firms became more attentive and informed about publicly available news about inflation, leading them to respond less to exogenously provided information about inflation and monetary policy. We also study the effects of RCTs in countries where inflation has been consistently high (Uruguay) and low (New Zealand) as well as what happens when the same agents are repeatedly provided information in both low‐ and high‐inflation environments (Italy). Our results broadly support models in which inattention is an endogenous outcome that depends on the economic environment.

Public disability insurance (DI) programs in many countries face growing fiscal pressures, prompting efforts to reduce spending. In this paper, we investigate the welfare effects of expanding the role of private insurance markets in the face of public DI cuts. We exploit a reform that abolished one part of German public DI and use unique data from a large insurer. We document modest crowding‐out effects of the reform, such that private DI take‐up remains incomplete. We find no adverse selection in the private DI market. Instead, private DI tends to attract individuals with high income, high education, and low disability risk. Using a revealed preference approach, we estimate individual insurance valuations. Our welfare analysis finds that partial DI provision via the voluntary private market can improve welfare. However, distributional concerns may justify a full public DI mandate.

This paper studies assortative matching in a non‐stationary search‐and‐matching model with non‐transferable payoffs. Non‐stationarity entails that the number and characteristics of agents searching evolve endogenously over time. Assortative matching can fail in non‐stationary environments under conditions for which Morgan (1995) and Smith (2006) show that it occurs in the steady state. This is due to the risk of worsening match prospects inherent to non‐stationary environments. The main contribution of this paper is to derive the weakest sufficient conditions on payoffs for which matching is assortative. In addition to known steady state conditions, more desirable individuals must be less risk‐averse in the sense of Arrow–Pratt.

We estimate the employment effects of a large program of public investment subsidies to private firms that ranked applicants on a score reflecting both objective rules and local politicians' discretion. Leveraging the rationing of funds as an ideal Regression Discontinuity Design, we characterize the heterogeneity of treatment effects and cost‐per‐new‐job across inframarginal firms and estimate the cost‐effectiveness of subsidies under factual and counterfactual allocations. Firms ranking high on objective rules and firms preferred by local politicians generated larger employment growth on average, but the latter did so at a higher cost per job. We estimate that relying only on objective criteria would reduce the cost per job by 11%, while relying only on political discretion would increase such cost by 42%.

This paper offers a strategic rationale for zero‐sum thinking in elections. We show that asymmetric information and distributional considerations together make voters wary of policies supported by others. This force impels a majority of voters to support policies contrary to their preferences and information. Our analysis identifies and interprets a form of “adverse correlation” that is necessary and sufficient for zero‐sum thinking to prevail in equilibrium.

Fiduciary duty aims to solve principal‐agent problems, and the United States is in the middle of a protracted debate surrounding the merits of extending it to all financial advisers. Leveraging a transaction‐level data set of deferred annuities and state‐level variation in common law fiduciary duty, we find that it raises risk‐adjusted returns by 25 bp and leads to a 16% decline in the entry of affected firms. Through the lens of a model of entry and advice provision, we show that this effect can be due to both an increase in fixed costs and an increase in the cost of providing low‐quality advice. We show how to disentangle these channels and find that both are empirically relevant. Counterfactual simulations show that further increases in the stringency of fiduciary duty monotonically improve advice quality.

The 2009 CARD Act limited credit card lenders' ability to raise borrowers' interest rates on the basis of new information. Pricing became less responsive to public and private signals of borrowers' risk and demand characteristics, and price dispersion fell by one‐third. I estimate the efficiency and distributional effects of this shift toward more pooled pricing. Prices fell for high‐risk and price‐inelastic consumers, but prices rose elsewhere in the market and newly exceeded willingness to pay for over 30% of the safest subprime borrowers. On net, average traded prices fell and consumer surplus rose at all credit scores. Higher consumer surplus was partly driven by a fall in lender profits, and partly by the Act's insurance value to borrowers who could retain favorable pricing after adverse changes to their default risk. The relatively high level of pre‐CARD‐Act markups was crucial for realizing these surplus gains.

We use the martingale construction of Luedtke and van der Laan (2016) to develop tests for the presence of treatment heterogeneity. The resulting sequential validation approach can be instantiated using various validation metrics, such as BLPs, GATES, QINI curves, etc., and provides an alternative to cross‐validation‐like cross‐fold application of these metrics. This note was prepared as a comment on the Fisher–Schultz paper by Chernozhukov, Demirer, Duflo, and Fernández‐Val, forthcoming in Econometrica.

Policymakers often choose a policy bundle that is a combination of different interventions in different dosages. We develop a new technique— treatment variant aggregation (TVA)—to select a policy from a large factorial design. TVA pools together policy variants that are not meaningfully different and prunes those deemed ineffective. This allows us to restrict attention to aggregated policy variants, consistently estimate their effects on the outcome, and estimate the best policy effect adjusting for the winner's curse. We apply TVA to a large randomized controlled trial that tests interventions to stimulate demand for immunization in Haryana, India. The policies under consideration include reminders, incentives, and local ambassadors for community mobilization. Cross‐randomizing these interventions, with different dosages or types of each intervention, yields 75 combinations. The policy with the largest impact (which combines incentives, ambassadors who are information hubs, and reminders) increases the number of immunizations by 44% relative to the status quo. The most cost‐effective policy (information hubs, ambassadors, and SMS reminders, but no incentives) increases the number of immunizations per dollar by 9.1% relative to the status quo.