Knowledge that Transforms

The control function approach is a convenient method of estimation in simultaneous equation systems. This requires that the system can be expressed in triangular form with variables satisfying a conditional mean independence restriction. Linear simultaneous models with additive errors can always be expressed in this form. However, in nonlinear nonadditive simultaneous systems, conditional independence requires a strong additional restriction known as control function separability. We argue that nonadditive models are a key characteristic of simultaneous models of economic behavior with unobserved heterogeneity. We review alternative “system” approaches and document the biases that occur when the control function approach is used inappropriately.

We analyze the optimal policy of an antitrust authority towards horizontal mergers when merger proposals are endogenous and firms choose among alternative mergers. In our model, the optimal policy of an antitrust authority that seeks to maximize expected consumer surplus imposes a tougher standard on “larger” mergers, i.e., those involving firms with a larger pre-merger market share. The optimal policy is a response to a bias in firms' proposal incentives: firms always propose a larger merger when it is better for consumers than a smaller one, but sometimes will propose the larger one even when it is worse for consumers.

A popular environmental policy is to pay forest owners for avoiding deforestation on their land. This is an example of “payments for ecosystem services” (PES). This paper shows that liquidity constraints can limit the effectiveness of PES programs. If an individual would have cut down trees to sell them, his opportunity costs are more front-loaded than the stream of PES income. If credit constrained, he might decline the program even if the net present value (NPV) of the PES income exceeds the NPV of his opportunity costs. I present evidence consistent with this prediction using data on forest owners in Uganda.

In August 2006, the Italian government released one-third of the nation's prison inmates via a national collective pardon. We test for a discontinuous break in national crime rates corresponding to the mass release. We also test for the effect of the return of the incarceration rate to its predicted steady state level on national crime rates. Finally, we exploit regional variation in prison releases based on the province of residence of pardoned inmates. All three sources of variation yield substantial incapacitation effect estimates and suggest that the crime-preventing effects of incarceration diminish with increases in the incarceration rate.

This paper argues that the possibility of bailouts to financial intermediaries distorts the supply price of capital and creates an argument for taxing financial bonuses separately from other sources of income. We develop a model of financial contracting where intermediaries compete for workers whose actions affect productivity and risk-taking in the financial sector. This derives the second-best optimum and market equilibrium. The optimal taxes that we propose increase both equity and efficiency compared to the pure market outcome.

A manager and a worker are in an infinitely repeated relationship in which the manager privately observes her opportunity costs of paying the worker. We show that the optimal relational contract generates periodic conflicts during which effort and expected profits decline gradually but recover instantaneously. To manage a conflict, the manager uses a combination of informal promises and formal commitments that evolves with the duration of the conflict. Finally, we show that liquidity constraints limit the manager's ability to manage conflicts but may also induce the worker to respond to a conflict by providing more effort rather than less.

The Bagwell and Staiger (1990) theory of cooperative trade agreements predicts new tariffs (i) increase with imports, (ii) increase with the inverse of the sum of the import demand and export supply elasticities, and (iii) decrease with the variance of imports. We find US import policy during 1997–2006 to be consistent with this theory. A one standard deviation increase in import growth, the inverse of the sum of the import demand and export supply elasticity, and the standard deviation of import growth changes the probability that the US imposes an antidumping tariff by 35 percent, by 88 percent, and by –76 percent, respectively.

The great housing convulsion that buffeted America between 2000 and 2010 has historical precedents, from the frontier land boom of the 1790s to the skyscraper craze of the 1920s. But this time was different. There was far less real uncertainty about fundamental economic and geographic trends, making the convulsion even more puzzling. During historic and recent booms, sensible models could justify high prices on the basis of seemingly reasonable projections about stable or growing prices. The recurring error appears to be a failure to anticipate the impact that elastic supply will eventually have on prices, whether for cotton in Alabama in 1820 or land in Las Vegas in 2006. Buyers don't appear to be irrational but rather cognitively limited investors who work with simple heuristic models, instead of a comprehensive general equilibrium framework. Low interest rates rarely seem to drive price growth; underpriced default options are a more common contributor to high prices. The primary cost of booms has not typically been overbuilding, but rather the financial chaos that accompanies housing downturns.

If trade barriers are managed by inefficient institutions, trade liberalization can lead to greater-than-expected gains. We examine Chinese textile and clothing exports before and after the elimination of externally imposed export quotas. Both the surge in export volume and the decline in export prices following quota removal are driven by net entry. This outcome is inconsistent with a model in which quotas are allocated based on firm productivity, implying misallocation of resources. Removing this misallocation accounts for a substantial share of the overall gain in productivity associated with quota removal.

The Federal Reserve's mandate has evolved considerably over the organization's hundred-year history. It was changed from an initial focus in 1913 on financial stability, to fiscal financing in World War II and its aftermath, to a strong anti-inflation focus from the late 1970s, and then back to greater emphasis on financial stability since the Great Contraction. Yet, as the Fed's mandate has expanded in recent years, its range of instruments has narrowed, partly based on a misguided belief in the inherent stability of financial markets. We argue for a return to multiple instruments, including a more active role for reserve requirements.