We propose a theory that analyzes how a workers’ asset holdings affect their job productivity. In a labor market with uninsurable risk, workers choose to direct their job search trading off productivity and wages against unemployment risk. Workers with low asset holdings have a precautionary job search motive, they direct their search to low productivity jobs because those offer a low risk at the cost of low productivity and a low wage. Our main theoretical contribution shows that the presence of consumption smoothing can reconcile the directed search model with negative duration-dependence on wages, a robust empirical regularity that the canonical directed search model cannot rationalize. We calibrate the infinite horizon economy and find this mechanism to be quantitatively important. We evaluate a tax financed unemployment insurance (UI) scheme and analyze how it affects welfare. Aggregate welfare is inverted U-shaped in benefits: the insurance effect UI dominates the incentive effects for low levels of benefits and vice versa for high benefits. In addition, when UI increases, total production falls in the economy while worker productivity increases.

Two cornerstones of empirical and policy analysis of firms, in macro, labor and industrial organization, are the determinants of the firm size distribution and the determinants of sorting between workers and firms. We propose a unifying theory of production where management resolves a tradeoff between hiring more versus better workers. The span of control or size is therefore intimately intertwined with the sorting pattern. We provide a condition for sorting that captures this tradeoff between the quantity and quality of workers and that generalizes Becker's sorting condition. A system of differential equations determines the equilibrium allocation, the firm size, and wages, and allows us to characterize the allocation of the quality and quantity of labor to firms of different productivity. We show that our model nests a large number of widely used existing models. We also augment the model to incorporate labor market frictions in the presence of sorting with large firms.

We investigate the role of search frictions in markets with price competition and how it leads to sorting of heterogeneous agents. There are two aspects of value creation: the match value when two agents actually trade and the probability of trading governed by the search technology. We show that positive assortative matching obtains when complementarities in the former outweigh complementarities in the latter. This happens if and only if the match-value function is root-supermodular, that is, its nth root is supermodular, where n reflects the elasticity of substitution of the search technology. This condition is weaker than the condition required for positive assortative matching in markets with random search.

Toward understanding assortative matching, this is a self-contained introduction to research on search and matching. We first explore the nontransferable and perfectly transferable utility matching paradigms, and then a unifying imperfectly transferable utility matching model. Motivated by some unrealistic predictions of frictionless matching, we flesh out the foundational economics of search theory. We then revisit the original matching paradigms with search frictions. We finally allow informational frictions that often arise, such as in college-student sorting.

We document the evolution of market power based on firm-level data for the U.S. economy since 1955. We measure both markups and profitability. In 1980, aggregate markups start to rise from 21% above marginal cost to 61% now. The increase is driven mainly by the upper tail of the markup distribution: the upper percentiles have increased sharply. Quite strikingly, the median is unchanged. In addition to the fattening upper tail of the markup distribution, there is reallocation of market share from low- to high-markup firms. This rise occurs mostly within industry. We also find an increase in the average profit rate from 1% to 8%. Although there is also an increase in overhead costs, the markup increase is in excess of overhead. We discuss the macroeconomic implications of an increase in average market power, which can account for a number of secular trends in the past four decades, most notably the declining labor and capital shares as well as the decrease in labor market dynamism.

We propose a theory of how market power affects wage inequality. We ask how goods and labor market power jointly determine the level of wages, the skill premium, and wage inequality. We then use detailed microdata from the U.S. Census Bureau between 1997 and 2016 to estimate the parameters of labor supply, technology, and the market structure. We find that a less competitive market structure lowers the average wage of high‐skilled workers by 11.3%, and of low‐skilled workers by 12.2%, contributes 8.1% to the rise in the skill premium, and accounts for 54.8% of the increase in between‐establishment wage variance.

An incentives based theory of policing is developed which can explain the phenomenon of random “crackdowns,” i.e., intermittent periods of high interdiction/surveillance. For a variety of police objective functions, random crackdowns can be part of the optimal monitoring strategy. We demonstrate support for implications of the crackdown theory using traffic data gathered by the Belgian Police Department and use the model to estimate the deterrence effect of additional resources spent on speeding interdiction.

We investigate the role of skill complementarities in production and mobility across cities. The nature of the complementarities determines the equilibrium skill distribution across cities. With extreme-skill complementarity, the skill distribution has thicker tails in large cities; with top-skill complementarity, there is first-order stochastic dominance. Using wage and housing price data, we find robust evidence of thick tails in large cities: large cities disproportionately attract both high- and low-skilled workers, while average skills are constant across city size. This pattern of spatial sorting is consistent with extreme-skill complementarity, where the productivity of high-skilled workers and of the providers of low-skilled services are mutually enhanced.

Should optimal income taxation change when firms have market power? We analyze how the planner can optimally tax labor income of workers and profits of entrepreneurs. We derive optimal tax rates that depend on markups and identify four distinct components: the Mirrleesian incentive effect, the Pigouvian tax correction of the negative externality of market power, redistribution through altered factor prices, and reallocation of output toward the most productive firms. We quantify the optimal tax for the US economy and provide concrete proposals how to use income taxation to redistribute income while incentivizing production in the presence of market power.