Contributions in Merlin

This paper introduces a new method for deriving covariance matrix estimators that are decision-theoretically optimal within a class of nonlinear shrinkage estimators. The key is to employ large-dimensional asymptotics: the matrix dimension and the sample size go to infinity together, with their ratio converging to a finite, nonzero limit. As the main focus, we apply this method to Stein’s loss. Compared to the estimator of Stein (1975, 1986), ours has five theoretical advantages: (1) it asymptotically minimizes the loss itself, instead of an estimator of the expected loss; (2) it does not necessitate post-processing via an ad hoc algorithm (called “isotonization”) to restore the positivity or the ordering of the covariance matrix eigenvalues; (3) it does not ignore any terms in the function to be minimized; (4) it does not require normality; and (5) it is not limited to applications where the sample size exceeds the dimension. In addition to these theoretical advantages, our estimator also improves upon Stein’s estimator in terms of finite-sample performance, as evidenced via extensive Monte Carlo simulations. To further demonstrate the effectiveness of our method, we show that some previously suggested estimators of the covariance matrix and its inverse are decision-theoretically optimal in the large-dimensional asymptotic limit with respect to the Frobenius loss function.

The presence of workers who reciprocate higher wages with greater effort can have important consequences for labor markets. Knowledge about the determinants of reciprocal effort choices is, however, incomplete. We investigate the role of fairness perceptions and social preferences in workers’ performance in a field experiment in which workers were hired for a one-time job. We show that workers who perceive being underpaid at the base wage increase their performance if the hourly wage increases, while those who feel adequately paid or overpaid at the base wage do not change their performance. Moreover, we find that only workers who display positive reciprocity in a lab experiment show reciprocal performance responses in the field, while workers who lack positive reciprocity in the lab do not respond to the wage increase even if they feel underpaid at the base wage. Our findings suggest that fairness perceptions and social preferences are key in workers’ performance response to a wage increase. They are the first direct evidence of the fair-wage effort hypothesis in the field and also help interpret previous contradictory findings in the literature.

As the first, substantive contribution, this paper revisits the effectiveness of two widely used public sponsored training programs, the first one focusing on intensive occupational training and the second one on short-term activation and job entry. We use an exceptionally rich administrative data set for Germany to estimate their employment and earnings effects in the early 2000s. We employ a stratified propensity score matching approach to address dynamic selection into heterogeneous programs. As a second, methodological contribution, we carefully assess to what extent various aspects of our empirical strategy such as conditioning flexibly on employment and benefit histories, the availability of rich personal information, handling of later program participations, and further methodological and specification choices affect estimation results. Our results imply pronounced negative lock-in effects in the short run in general and positive medium-run effects on employment and earnings when job-seekers enroll after having been unemployed for some time. We find that data and specification issues can have a large effect on impact estimates.

This paper examines the relationship between parenthood and life satisfaction using longitudinal data on women from the German Socio-Economic Panel. Previous studies have focused on satisfaction differences between parents and comparable childless adults, mostly finding small and often negative effects of parenthood. These comparisons of ex-post similar individuals are problematic if a self-selection into motherhood exists. In this study we examine the selection issue in detail by exploiting the extended longitudinal dimension of the panel to track self-reported life satisfaction of women eventually to become mothers and of women eventually attaining a completed fertility of zero. We document that these groups' satisfaction paths diverge around five years before mothers' first birth, even after adjusting for differences in observables. In our estimations, we employ matching and regression techniques which account for this selection into motherhood. We find motherhood to be associated with substantial positive satisfaction gains.

Standard economic models view risk taking and time discounting as two independent dimensions of decision makers' behavior. However, mounting experimental evidence demonstrates the existence of robust and systematic interaction effects. There are striking parallels in patterns of risk taking and time discounting behavior, which suggests that there is a common underlying force driving these interactions. Here we show that decision makers' anticipation of something going wrong in the future conjointly with their proneness to probability weighting generates a unifying framework for explaining seven puzzling regularities: delay-dependent risk tolerance, aversion to sequential resolution of uncertainty, preferences for resolution timing, hyperbolic discounting, subadditive discounting, the differential discounting of risky and certain outcomes, and the order dependence of prospect valuation. Finally, we discuss the implications of our framework for understanding real-world behavior, such as the coexistence of underinsuring and overinsuring.

Understanding differences in business cycle phenomena between Emerging Market Economies (EMEs) and industrialized countries has been at the center of recent research on macroeconomic fluctuations. The purpose of this paper is to investigate the importance of certain credit market imperfections in different EMEs. To this end, we develop a small open economy Dynamic Stochastic General Equilibrium (DSGE) framework featuring both permanent and transitory productivity shocks, differentiated home and foreign goods, and endogenous exchange rate movements. Furthermore, our model incorporates liability dollarization as a particular form of financial frictions in EMEs. In this vein, we account for the fact that emerging markets traditionally have had difficulties in borrowing in domestic currency on international capital markets and thus allow for valuation effects in our analysis. We estimate our model using Bayesian techniques for a number of EMEs and thereby control for potential heterogeneity across countries. Contrary to previous studies in this strand of the literature, we include a (vector-)autoregressive measurement error component to capture off-model dynamics. Regarding business cycles in emerging markets, our main findings are that (i) even though we incorporate financial frictions in the framework, trend shocks are the main determinant of macroeconomic fluctuations, (ii) accounting for liability dollarization ameliorates the model fit, and (iii) valuation effects on average stabilize changes in the net foreign asset position.

Das Geschehen auf den Finanzmärkten hängt vom individuellen Verhalten ab, wird aber auch wesentlich bestimmt durch die Ausgestaltung des Finanzsystems, das heisst durch die Rollen, die den einzelnen Akteure zugewiesen werden, und durch die Regeln für die Interaktion der verschiedenen Rollen. Diese Arbeit behandelt nach einleitenden methodischen Vorbemerkungen zunächst die Frage der Verantwortung im gesamtwirtschaftlichen System (Kapitel 2) und beschäftigt sich dann mit der Verantwortung von einflussreichen Rollen und Subsystemen der Wirtschaft. Insbesondere wird diskutiert, was Verantwortung für die Ökonomie und die Finance als wissenschaftliches Disziplin bedeutet (Kapitel 3). Kapitel 4 setzt sich mit dem Finanzsystem auseinander und argumentiert, dass eine Inflation an Finanzprodukten und Finanztransaktionen zu Konfusion und negativen externen Effekten führt, die das Marktgeschehen in der realen Wirtschaft und im Finanzsektor stören. Im abschliessenden fünften Kapitel werden politische Massnahmen zur Herstellung von Ordnung im Finanzsystem dargelegt.

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.