Knowledge that Transforms

We often deal with uncertain events for which no probabilities are known. Several normative models have been proposed. Descriptive studies have usually been qualitative, or they estimated ambiguity aversion through one single number. This paper introduces the source method, a tractable method for quantitatively analyzing uncertainty empirically. The theoretical key is the distinction between different sources of uncertainty, within which subjective (choice-based) probabilities can still be defined. Source functions convert those subjective probabilities into willingness to bet. We apply our method in an experiment, where we do not commit to particular ambiguity attitudes but let the data speak.

Evidence from a nationally representative sample of households illuminates the determinants of recycling behavior for plastic water bottles. Private values of the environment are influential in promoting recycling, as are personal norms for pro-environmental behavior. However, social norms with respect to the assessment of the household's recycling behaviors by others have little independent effect. Particularly influential are policies that create economic incentives to promote recycling either through state recycling laws that reduce the time and inconvenience costs of recycling or through bottle deposits. Effective policies can have a discontinuous effect at the individual level, transforming non-recyclers into avid recyclers.

We study the purchasing power parity (PPP) puzzle in a multi-sector, two-country, sticky-price model. Across sectors, firms differ in the extent of price stickiness, in accordance with recent microeconomic evidence on price setting in various countries. Combined with local currency pricing, this leads sectoral real exchange rates to have heterogeneous dynamics. We show analytically that in this economy, deviations of the real exchange rate from PPP are more volatile and persistent than in a counterfactual one-sector world economy that features the same average frequency of price changes, and is otherwise identical to the multi-sector world economy. When simulated with a sectoral distribution of price stickiness that matches the microeconomic evidence for the U.S. economy, the model produces a half-life of deviations from PPP of 39 months. In contrast, the half-life of such deviations in the counterfactual one-sector economy is only slightly above one year. As a by-product, our model provides a decomposition of this difference in persistence that allows a structural interpretation of the different approaches found in the empirical literature on aggregation and the real exchange rate. In particular, we reconcile the apparently conflicting findings that gave rise to the "PPP Strikes Back debate" (Imbs et al. 2005a,b and Chen and Engel 2005).

I study a dynamic model of trial-and-error search in which agents do not have complete knowledge of how choices are mapped into outcomes. Agents learn about the mapping by observing the choices of earlier agents and the outcomes that are realized. The key novelty is that the mapping is represented as the realized path of a Brownian motion. I characterize for this environment the optimal behavior each period as well as the trajectory of experimentation and learning through time. Applied to new product development, the model shares features of the data with the well-known Product Life Cycle.

Is lifetime inequality mainly due to differences across people established early in life or to differences in luck experienced over the working lifetime? We answer this question within a model that features idiosyncratic shocks to human capital, estimated directly from data, as well as heterogeneity in ability to learn, initial human capital, and initial wealth. We find that, as of age 23, differences in initial conditions account for more of the variation in lifetime earnings, lifetime wealth, and lifetime utility than do differences in shocks received over the working lifetime.

Do women perform worse than equally able men in stressful competitive settings? We ask this question for competitions with a high payoff—admissions to tuition-free selective universities. With data on an entire cohort of Czech students graduating from secondary schools and applying to universities, we show that, compared to men of similar general skills and subject-of-study preferences, women perform similarly well when competition is less intense, but perform substantially worse (are less likely to be admitted) when applying to very selective universities.

We present empirical evidence that, among a variety of cultural dimensions, the individualism-collectivism dimension, based on Hofstede's (2001) data, is the most important and robustly significant effect of culture on long run growth. Other dimensions that have a significant effect, albeit less robust, are generally strongly correlated with individualism and convey similar information. We found no significant or robust effect on growth from cultural dimensions that are independent from the individualism-collectivism cleavage.

Machina (2009) introduced two examples that falsify Choquet expected utility, presently one of the most popular models of ambiguity. This article shows that Machina's examples falsify not only the model mentioned, but also four other popular models for ambiguity of the literature, namely maxmin expected utility, variational preferences, α-maxmin, and the smooth model of ambiguity aversion. Thus, Machina's examples pose a challenge to most of the present field of ambiguity. Finally, the paper discusses how an alternative representation of ambiguity-averse preferences works to accommodate the Machina paradoxes and what drives the results.

Economic models that do not incorporate financial frictions only explain about 70 to 80 percent of the decline in world trade that occurred in the 2008–2009 crisis. We review evidence that shows financial factors also contributed to the great trade collapse and uncover two new stylized facts in support of it. First, we show that the prices of manufactured exports rose relative to domestic prices during the crisis. Second, we show that US seaborne exports and imports, which are likely to be more sensitive to trade finance problems, saw their prices rise relative to goods shipped by air or land.

We construct a family model of labor supply that features adjustment along both the intensive and extensive margin. Intensive margin adjsutment is restricted to two values: full-time work and part-time work. Using simulated data from the steady state of the calibrated model, we examine whether standard labor supply regressions can uncover the true value of the intertemporal elasticity of labor supply parameter. We find positive estimated elasticities that are larger for women and that are highly significant, but they bear virtually no relationship to the underlying preference parameters.