Knowledge that Transforms

We study the pure‐strategy subgame‐perfect Nash equilibria of stochastic games with perfect monitoring, geometric discounting, and public randomization. We develop novel algorithms for computing equilibrium payoffs, in which we combine policy iteration when incentive constraints are slack with value iteration when incentive constraints bind. We also provide software implementations of our algorithms. Preliminary simulations indicate that they are significantly more efficient than existing methods. The theoretical results that underlie the algorithms also imply bounds on the computational complexity of equilibrium payoffs when there are two players. When there are more than two players, we show by example that the number of extreme equilibrium payoffs may be countably infinite.

This research advances the hypothesis and establishes empirically that interpersonal population diversity, rather than fractionalization or polarization across ethnic groups, has been pivotal to the emergence, prevalence, recurrence, and severity of intrasocietal conflicts. Exploiting an exogenous source of variations in population diversity across nations and ethnic groups, as determined predominantly during the exodus of humans from Africa tens of thousands of years ago, the study demonstrates that population diversity, and its impact on the degree of diversity within ethnic groups, has contributed significantly to the risk and intensity of historical and contemporary civil conflicts. The findings arguably reflect the contribution of population diversity to the non-cohesivnesss of society, as reflected partly in the prevalence of mistrust, the divergence in preferences for public goods and redistributive policies, and the degree of fractionalization and polarization across ethnic, linguistic, and religious groups.

Cumulative Prospect Theory (CPT), the leading behavioral account of decisionmaking under uncertainty, avoids the dominance violations implicit in Prospect Theory (PT) by assuming that the probability weight applied to a given outcome depends on its ranking. We devise a simple and direct nonparametric method for measuring the change in relative probability weights resulting from a change in payoff ranks. We find no evidence that these weights are even modestly sensitive to ranks. Conventional calibrations of CPT preferences imply that the percentage change in probability weights should be an order of magnitude larger than we observe. It follows either that probability weighting is not rank‐dependent, or that the weighting function is nearly linear. Nonparametric measurement of the change in relative probability weights resulting from changes in probabilities rules out the second possibility. Additional tests nevertheless indicate that the dominance patterns predicted by PT do not arise. We reconcile these findings by positing a form of complexity aversion that generalizes the well‐known certainty effect.

In this paper, we develop a model that captures key components of the Roy model, a search model, compensating differentials, and human capital accumulation on‐the‐job. We establish which components of the model can be non‐parametrically identified and which ones cannot. We estimate the model and use it to assess the relative contribution of the different factors for overall wage inequality. We find that variation in premarket skills (the key feature of the Roy model) is the most important component to account for the majority of wage variation. We also demonstrate that there is substantial interaction between the other components, most notably, that the importance of the job match obtained by search frictions varies from around 4% to around 29%, depending on how we account for other components. Inequality due to preferences for non‐pecuniary aspects of the job (which leads to compensating differentials) and search are both very important for explaining other features of the data. Search is important for turnover, but so are preferences for non‐pecuniary aspects of jobs as one‐third of all choices between two jobs would have resulted in a different outcome if the worker only cared about wages.

Differences in regulated pharmaceutical prices within the European Economic Area create arbitrage opportunities that pharmacy retailers can access through parallel imports. For prescription drugs under patent, parallel trade affects the sharing of profits among an innovating pharmaceutical company, retailers, and parallel traders. We develop a structural model of demand and supply in which retailers can choose the set of goods to sell, thus foreclosing consumers' access to less profitable drugs. This allows retailers to bargain and obtain lower wholesale prices from the manufacturer and parallel trader. With detailed transaction data from Norway, we identify a demand model with unobserved choice sets using retail‐side conditions for optimal assortment decisions of pharmacies. We find that retailer incentives play a significant role in fostering parallel trade penetration and that banning parallel imports would benefit manufacturers as well as prevent pharmacies from foreclosing the manufacturer's product. Finally, in the case of the statin market in Norway, we show that it would be possible to decrease spending and increase profits of the original manufacturer through lump sum transfers associated with a lower reimbursement price, thus decreasing price differentiation across countries.

Do new communication technologies, such as social media, alleviate the collective action problem? This paper provides evidence that penetration of VK, the dominant Russian online social network, led to more protest activity during a wave of protests in Russia in 2011. As a source of exogenous variation in network penetration, we use the information on the city of origin of the students who studied with the founder of VK, controlling for the city of origin of the students who studied at the same university several years earlier or later. We find that a 10% increase in VK penetration increased the probability of a protest by 4.6% and the number of protesters by 19%. Additional results suggest that social media induced protest activity by reducing the costs of coordination rather than by spreading information critical of the government. We observe that VK penetration increased pro‐governmental support, with no evidence of increased polarization. We also find that cities with higher fractionalization of network users between VK and Facebook experienced fewer protests, and the effect of VK on protests exhibits threshold behavior.

We study how aggregate economic conditions affect the timing of marriage, and particularly child marriage, in Sub‐Saharan Africa and in India. In both regions, substantial monetary or in‐kind transfers occur with marriage: bride price across Sub‐Saharan Africa and dowry in India. In a simple equilibrium model of the marriage market in which parents choose when their children marry, income shocks affect the age of marriage because marriage payments are a source of consumption smoothing, particularly for a woman's family. As predicted by our model, we show that droughts, which reduce annual crop yields by 10 to 15% and aggregate income by 4 to 5%, have opposite effects on the marriage behavior of a sample of 400,000 women in the two regions: in Sub‐Saharan Africa they increase the annual hazard into child marriage by 3%, while in India droughts reduce such a hazard by 4%. Changes in the age of marriage due to droughts are associated with changes in fertility, especially in Sub‐Saharan Africa, and with declines in observed marriage payments. Our results indicate that the age of marriage responds to short‐term changes in aggregate economic conditions and that marriage payments determine the sign of this response. This suggests that, in order to design successful policies to combat child marriage and improve investments in daughters' human capital, it is crucial to understand the economic role of marriage market institutions.

Most of the literature that studies frictional search‐and‐matching models with heterogeneous agents and random search investigates steady state equilibria. Steady state equilibrium requires, in particular, that the flows of agents into and out of the population of unmatched agents balance. We investigate the structure of this balance condition, taking agents' matching behavior as given. Building on the “fundamental matching lemma” for quadratic search technologies in Shimer and Smith (2000), we establish existence, uniqueness, and comparative statics properties of the solution to the balance condition for any search technology satisfying minimal regularity conditions. Implications for the existence and structure of steady state equilibria in the Shimer–Smith model and extensions thereof are noted. These reinforce the point that much of the structure of search‐and‐matching models with quadratic search technologies carries over to more general search technologies.

We study a model of cheap talk with one substantive assumption: The sender's preferences are state independent. Our main observation is that such a sender gains credibility by degrading self‐serving information. Using this observation, we examine the sender's benefits from communication, assess the value of commitment, and explicitly solve for sender‐optimal equilibria in three examples. A key result is a geometric characterization of the value of cheap talk, described by the quasi concave envelope of the sender's value function.

We propose a new theory of price rigidity based on firms' Knightian uncertainty about their competitive environment. This uncertainty has two key implications. First, firms learn about the shape of their demand function from past observations of quantities sold. This learning gives rise to kinks in the expected profit function at previously observed prices, making those prices both sticky and more likely to reoccur. Second, uncertainty about the relationship between aggregate and industry‐level inflation generates nominal rigidity. We prove the main insights analytically and quantify the effects of our mechanism. Our estimated quantitative model is consistent with a wide range of micro‐level pricing facts that are typically challenging to match jointly. It also implies significantly more persistent monetary non‐neutrality than in standard models, allowing it to generate large real effects from nominal shocks.