Knowledge that Transforms

To determine the welfare implications of price changes in demand data, we introduce a revealed preference relation over prices. We show that the absence of cycles in this relation characterizes a consumer who trades off the utility of consumption against the disutility of expenditure. Our model can be applied whenever a consumer’s demand over a strict subset of all available goods is being analysed; it can also be extended to settings with discrete goods and non-linear prices. To illustrate its use, we apply our model to a single-agent data set and to a data set with repeated cross-sections. We develop a novel test of linear hypotheses on partially identified parameters to estimate the proportion of the population who are revealed better off due to a price change in the latter application. This new technique can be used for non-parametric counterfactual analysis more broadly.

We incorporate the lumpy nature of firm-level investment into the study of how tax policy affects investment behaviour. We show that tax policies can directly impact the lumpiness of investment. Extensive-margin responses to tax policy are key to understanding the effects of different tax reforms and to designing effective stimulus policies. We illustrate these results by studying China’s 2009 VAT reform, which lowered the tax cost of investment and reduced partial irreversibility—the price gap between new and used capital. Using comprehensive tax survey data and a difference-in-differences design, we estimate a 36% relative investment increase that is driven by investment spikes. Using a dynamic investment model that fits the reduced-form effects of the reform, we show that policies that directly reduce the likelihood of firm inaction are more effective at stimulating investment.

Borrowers obtain liquidity by issuing securities backed by the current period payoff and resale price of a long-lived collateral asset, and they are privately informed about the payoff distribution. Asset price can be self-fulfilling: a higher asset price lowers adverse selection and allows borrowers to raise greater funding, which makes the asset more valuable, leading to multiple equilibria. Optimal security design eliminates multiple equilibria, improves welfare, and can be implemented as a repo contract. Persistent adverse selection lowers debt funding, generates volatility in asset prices, and exacerbates credit crunches. The theory demonstrates the role of asset-backed securities on stability of market-based financial systems.

Motivated by the prevalence of simultaneous bidding across a wide range of auction markets, we develop and estimate a model of strategic interaction in simultaneous first-price auctions when objects are heterogeneous and bidders have non-additive preferences over combinations. We establish non-parametric identification of primitives in this model under standard exclusion restrictions, providing a basis for both estimation and testing of preferences over combinations. We then apply our model to data on Michigan Department of Transportation (MDOT) highway procurement auctions, quantifying the magnitude of cost synergies and evaluating the performance of the simultaneous first-price mechanism in the MDOT marketplace.

We study dynamic matching in exchange markets with easy- and hard-to-match agents. A greedy policy, which attempts to match agents upon arrival, ignores the positive externality that waiting agents provide by facilitating future matchings. We prove that the trade-off between a “thicker” market and faster matching vanishes in large markets; the greedy policy leads to shorter waiting times and more agents matched than any other policy. We empirically confirm these findings in data from the National Kidney Registry. Greedy matching achieves as many transplants as commonly used policies (1.8% more than monthly batching) and shorter waiting times (16 days faster than monthly batching).

A patient seller interacts with a sequence of myopic consumers. Each period, the seller chooses the quality of his product, and a consumer decides whether to trust the seller after she observes the seller’s actions in the last K periods (limited memory) and at least one previous consumer’s action (observational learning). However, the consumer cannot observe the seller’s action in the current period. With positive probability, the seller is a commitment type who plays his Stackelberg action in every period. I show that under limited memory and observational learning, consumers are concerned that the seller will not play his Stackelberg action when he has a positive reputation and will play his Stackelberg action after he has lost his reputation. Such a concern leads to equilibria where the seller receives a low payoff from building a reputation. I also show that my reputation failure result hinges on consumers’ observational learning.

I study unemployment insurance (UI) in general equilibrium with incomplete markets, search frictions, and nominal rigidities. An increase in generosity raises the aggregate demand for consumption if the unemployed have a higher marginal propensity to consume than the employed or if agents precautionary save in light of future income risk. This raises output and employment unless monetary policy raises the nominal interest rate. In an analysis of the U.S. economy over 2008–2014, UI benefit extensions had a contemporaneous output multiplier around 1. The unemployment rate would have been as much as 0.4 pp higher absent these extensions.

Housing affordability is the main policy challenge for most large cities in the world. Zoning changes, rent control, housing vouchers, and tax credits are the main levers employed by policymakers. How effective are they at combatting the affordability crisis? We build a dynamic stochastic spatial equilibrium model to evaluate the effect of these policies on the well-being of its citizens. The model endogenizes house prices, rents, construction, labour supply, output, income, and wealth inequality, the location decisions of households within the city as well as inter-city migration. Its main novel features are risk, risk aversion, and incomplete risk-sharing. We calibrate the model to the New York metropolitan statistical area. Housing affordability policies carry substantial insurance value but affect aggregate housing and labour supply and cause misallocation in labour and housing markets. Housing affordability policies that enhance access to this insurance especially for the neediest households create substantial net welfare gains.

Growth has fallen in the U.S. amid a rise in firm concentration. Market share has shifted to low labour share firms, while within-firm labour shares have actually risen. We propose a theory linking these trends in which the driving force is falling overhead costs of spanning multiple products or a rising efficiency advantage of large firms. In response, the most efficient firms (with higher markups) spread into new product lines, thereby increasing concentration and generating a temporary burst of growth. Eventually, due to greater competition from efficient firms, within-firm markups and incentives to innovate fall. Thus our simple model can generate qualitative patterns in line with the observed trends.

Financial sector wages have increased extraordinarily over the last decades. We address two potential explanations for this increase: (1) rising demand for talent and (2) firms sharing rents with their employees. Matching administrative data of Swedish workers, which include unique measures of individual talent, with financial information on their employers, we find no evidence that talent in finance improved, neither on average nor at the top. The increase in relative finance wages is present across talent and education levels, which together can explain at most 20% of it. In contrast, rising financial sector profits that are shared with employees account for up to half of the relative wage increase. The limited labour supply response may partly be explained by the importance of early-career entry and social connections in finance. Our findings alleviate concerns about “brain drain” into finance but suggest that finance workers have captured rising rents over time.