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Increasingly, algorithms are supplanting human decision-makers in pricing goods and services. To analyze the possible consequences, we study experimentally the behavior of algorithms powered by Artificial Intelligence (Q-learning) in a workhorse oligopoly model of repeated price competition. We find that the algorithms consistently learn to charge supracompetitive prices, without communicating with one another. The high prices are sustained by collusive strategies with a finite phase of punishment followed by a gradual return to cooperation. This finding is robust to asymmetries in cost or demand, changes in the number of players, and various forms of uncertainty.

Why do prices in Spain's regions fail to converge? The prime suspects for this puzzling result are differences in regional barriers to entry in retail distribution. This paper develops a Cournot-Nash model of imperfect competition to illustrate the effect of barriers on prices. A unique data set-derived from an extensive analysis of competition policies in Spain- provides evidence that barriers to entry increase regional prices. The evidence also suggests that, consistent with the model's predictions, barriers to entry raise prices up to a point, and thus indicate that barriers have a threshold effect on prices.

This paper develops a general theory of aggregation in inefficient economies. We provide nonparametric formulas for aggregating microeconomic shocks in economies with distortions such as taxes, markups, frictions to resource reallocation, financial frictions, and nominal rigidities. We allow for arbitrary elasticities of substitution, returns to scale, factor mobility, and input-output network linkages. We show how to separately measure changes in technical and allocative efficiency. We also show how to compute the social cost of distortions. We pursue applications focusing on firm-level markups in the United States. We find that improvement in allocative efficiency, due to the reallocation over time of market share to high-markup firms, accounts for about half of aggregate TFP growth over the period 1997–2015. We also find that eliminating the misallocation resulting from the large and dispersed markups estimated in the data would raise aggregate TFP by about 15%, increasing the economy-wide cost of monopoly distortions by two orders of magnitude compared with the famous 0.1% estimate by Harberger (1954). These exact numbers should be interpreted with care because the data are imperfect and require substantial imputation.

Empirical work has drawn attention to the high degree of productivity differences within industries and their role in resource allocation. This paper examines the allocational efficiency of suchmarkets. Productivity differences introduce two new margins of potential inefficiency: selection of the right distribution of firms and allocation of the right quantities across firms. We show that these considerations affect welfare and policy analysis, and market power across firms leads to distortions in resource allocation. Demand-side elasticities determine how resources are misallocated and when increased competition from market expansion provides welfare gains.

This article assesses several aspects of recent macroeconomic market power research. These include the ways market power is defined and measured; the use of accounting data to estimate markups; the quantitative implications of theoretical connections among markups, prices, costs, scale elasticities, and profits; and conflicting evidence on whether greater market power has led to lower investment rates and a lower labor share of income. Throughout this discussion, I characterize the congruencies and incongruencies between macro evidence and micro views of market power and, when they do not perfectly overlap, explain the open questions that need to be answered to make the connection complete.

This article considers the recent literature on firm markups in light of both new and classic work in the field of industrial organization. We detail the shortcomings of papers that rely on discredited approaches from the \"structure-conduct-performance\" literature. In contrast, papers based on production function estimation have made useful progress in measuring broad trends in markups. However, industries are so heterogeneous that careful industry-specific studies are also required, and sorely needed. Examples of such studies illustrate differing explanations for rising markups, including endogenous increases in fixed costs associated with lower marginal costs. In some industries there is evidence of price increases driven by mergers. To fully understand markups, we must eventually recover the key economic primitives of demand, marginal cost, and fixed and sunk costs. We end by discussing the various aspects of antitrust enforcement that may be of increasing importance regardless of the cause of increased markups.

Most assets are traded in multiple interconnected trading venues. This paper develops an equilibrium model of decentralized markets that accommodates general market structures with coexisting exchanges. Decentralized markets can allocate risk among traders with different risk preferences more efficiently, thus realizing gains from trade that cannot be reproduced in centralized markets. Market decentralization always increases price impact. Yet, markets in which assets are traded in multiple exchanges, whether they are disjoint or intermediated, can give higher welfare than the centralized market with the same traders and assets. In decentralized markets, demand substitutability across assets is endogenous and heterogeneous among traders.

This paper considers cost-reducing R&D investment with spillovers in a Cournot oligopoly with overlapping ownership. We show that overlapping ownership leads to internalization of rivals’ profits by firms and find that, for demand not too convex, increases in overlapping ownership increase (decrease) R&D and output for high (low) enough spillovers while they increase R&D but decrease output for intermediate levels of spillovers. There is scope for overlapping ownership to improve welfare and consumer surplus, provided that spillovers are sufficiently large. The results obtained are robust when R&D has commitment value and in a Bertrand oligopoly model with product differentiation.

A number of recent papers have argued that US firms exert increasing market power, as measured by their markups of price over marginal cost. I review three of the main approaches to estimating economy-wide markups and show that all are based on the hypothesis of firm cost minimization. Yet different assumptions and methods of implementation lead to quite different conclusions regarding the levels and trends of markups. I survey the literature critically and argue that some of the startling findings of steeply rising markups are difficult to reconcile with other evidence and with aggregate data. Existing methods cannot determine whether markups have been stable or whether they have risen modestly over the past several decades. Even relatively small increases in markups are consistent with significant changes in aggregate outcomes, such as the observed decline in labor's share of national income.

We investigate the effects of price discrimination on prices, profits, and consumer surplus when (a) at least one competing firm can use consumers’ private information to price discriminate yet (b) consumers can prevent such use by paying a “privacy cost.” Unlike a monopolist, competing duopolists do not always benefit from a higher privacy cost because each firm’s profit decreases—and consumer surplus increases—with that cost. Under such competition, the optimal strategy for an owner of consumer data that sells information in a single block is selling to only one firm, thereby maximizing the stakes for rival buyers. The resulting inefficiencies imply that policy makers should devote more attention to discouraging exclusivity deals and less to ensuring that consumers can easily protect their privacy. The online appendix is available at https://doi.org/10.1287/mnsc.2017.2989 . This paper was accepted by J. Miguel Villas-Boas, marketing.