Contributions in Merlin

In small groups, norm enforcement is achieved through mutual punishment and reward. In large societies, norms are enforced by specialists such as government officials. However, not every public cause is overseen by states, for instance those organized at the international level. This paper shows how non-governmental norm enforcement can emerge as a decentralized equilibrium. As a first stage, individuals voluntarily contribute to a non-governmental agency that produces an incentive system. The second stage is the provision of a public good on the basis of private contributions. The incentive system punishes and rewards deviations from the norm for contributions by means of public approval or disapproval of behavior. It is shown that, even in large populations, nongovernmental norm enforcement can be supported in a non-cooperative equilibrium of utility-maximizing individuals.

We construct a fully specified extensive form game that aptures competitive markets with adverse selection. In articular, it allows firms to offer any finite set of contracts, so that cross-subsidization is not ruled out. Moreover, firms can withdraw from the market after initial contract offers have been observed. We show that a subgame perfect equilibrium always exists and that, in fact, when withdrawal is costless, the set of subgame perfect equilibrium outcomes may correspond to the entire set of feasible contracts. We then focus on robust equilibria that exist both when withdrawal costs are zero and when they are arbitrarily small but strictly positive. We show that the Miyazaki-Wilson contracts are the unique robust equilibrium outcome of our game. This outcome is always constrained efficient and involves cross-subsidization from low to high risk agents that is increasing in the share of low risks in the population under weak conditions on risk preferences.

We study the stability of voluntary cooperation in response to varying group growth rates. Using a laboratory public-good game, we construct a situation where increasing group size yields potential efficiency gains, but only with sustained cooperation. We then study the effect of exogenously varying growth rates on cooperation. Slow growth yields higher cooperation rates and welfare than fast growth, both for incumbents and entrants, which is consistent with optimistic self-reinforcing beliefs persisting under slower growth. Allowing incumbent group members to select growth rates also sustains high cooperation rates, but growth stalls at intermediate group sizes, leaving potential efficiency gains unrealized.

Covariance matrix estimation and principal component analysis (PCA) are two cornerstones of multivariate analysis. Classic textbook solutions perform poorly when the dimension of the data is of a magnitude similar to the sample size, or even larger. In such settings, there is a common remedy for both statistical problems: nonlinear shrinkage of the eigenvalues of the sample covariance matrix. The optimal nonlinear shrinkage formula depends on unknown population quantities and is thus not available. It is, however, possible to consistently estimate an oracle nonlinear shrinkage, which is motivated on asymptotic grounds. A key tool to this end is consistent estimation of the set of eigenvalues of the population covariance matrix (also known as the spectrum), an interesting and challenging problem in its own right. Extensive Monte Carlo simulations demonstrate that our methods have desirable finite-sample properties and outperform previous proposals.

In this paper we analyze R&D collaboration networks in industries where firms are competitors in the product market. Firms’ benefits from collaborations arise by sharing knowledge about a cost-reducing technology. By forming collaborations, however, firms also change their own competitive position in the market as well as the overall market structure. We analyze incentives of firms to form R&D collaborations with other firms and the implications of these alliance decisions for the overall network structure. We provide a general characterization of both equilibrium networks and endogenous production choices, and compare it to the efficient network architecture. We also allow for firms to differ in their technological characteristics, investigate how this affects their propensity to collaborate and study the resulting network architecture.

Many postulated relations in finance imply that expected asset returns strictly increase in an underlying characteristic. To examine the validity of such a claim, one needs to take the entire range of the characteristic into account, as is done in the recent proposal of Patton and Timmermann (2010). But their test is only a test for the direction of monotonicity, since it requires the relation to be monotonic from the outset: either weakly decreasing under the null or strictly increasing under the alternative. When the relation is non-monotonic or weakly increasing, the test can break down and falsely ‘establish’ a strictly increasing relation with high probability. We offer some alternative tests that do not share this problem. The behavior of the various tests is illustrated via Monte Carlo studies. We also present empirical applications to real data.

Many governments subsidize regional rail service as an alternative to road traffic. This paper assesses whether increases in service frequency reduce road traffic externalities. We exploit differences in service frequency growth by procurement mode following a railway reform in Germany to address endogeneity of service growth. Increases in service frequency reduce the number of severe road traffic accidents, carbon monoxide, nitrogen monoxide, nitrogen dioxide pollution and infant mortality. Placebo regressions with sulfur dioxide and ozone yield no effect. Service frequency growth between 1994 and 2004 improves environmental quality by an amount that is worth approximately 28-40 % of total subsidies. An analysis of household behavior shows that the effects of railway services on outcome variables are driven by substitution from road to rail.

This paper describes and analyzes research on the dynamics of long-term care and suggests directions for the literature to make progress. We discuss sources and causes of dynamics including inertia/state dependence (confounded by unobserved heterogeneity); match-specific effects; and costs of changing caregivers. We comment on causes of dynamics including learning/human capital accumulation; burnout; and game-playing. We suggest how to deal with endogenous geography; dynamics in discrete and continuous choices; and equilibrium issues (multiple equilibria, dynamic equilibria). Next, we evaluate the advantages of different potential data sources (NLTCS, PSID, AHEAD/HRS, SHARE, ELSA) and identify first order data problems including noisy measures of wealth and family structure. We suggest some methods to handle econometric problems such as endogeneity (work, geography) and measurement error. Finally, we discuss potential policy implications of dynamics including the effect of dynamics on parameter estimates and direct policy implications of inertia (implications for family welfare, parent welfare, child welfare, and cost of government programs).

This paper investigates empirically how similarity of demand structures - approximated by similarity of income distributions - affects trade patterns along both the extensive and intensive margin. The idea that similarity of demand structures intensifies trade goes back to the well-known Linder hypothesis. Based on a sample of 102 countries, I find that bilateral trade volumes are increasing in the overlap of two countries income distributions. This effect is driven by both the extensive and intensive margin. I establish two novel measures of income similarity - the average income level of the overlap area and the range of incomes for which two distributions overlap - and document that both are important determinants of bilateral trade margins. My analysis shows that the positive relationship between similarity of income distributions and bilateral trade margins is present at the aggregate and disaggregate level of trade flows.

We assess the role of financial linkages in the transmission of sovereign risk in the Euro Crisis. Building on the narrative approach by Romer and Romer (1989), we use financial news to identify structural shocks in a vector autoregressive model of daily sovereign CDS premia for eleven European countries. To estimate how these shocks transmit across borders, we use data on cross-country bank exposures to sovereign debt. Our results indicate that exposure to Greek sovereign debt and the debt of Greek banks constitute important transmission channels. All else being equal, the transmission rate to the country with the greatest exposure to Greece (1.22 percent of GDP) has been roughly 46 percent higher than the rate to the country with the least exposure (0.08 percent of GDP).