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In repeated normal-form (simultaneous-move) games, simple penal codes (Abreu, 1986, 1988) permit an elegant characterization of the set of subgame-perfect outcomes. We show that the logic of simple penal codes fails in repeated extensive-form games. By means of examples, we identify two types of settings in which a subgame-perfect outcome may be supported only by a profile with the property that the continuation play after a deviation is tailored not only to the identity of the deviator, but also to the nature of the deviation. Download Paper
We develop a theory of multiproduct firms to analyze the  effects of globalization on the distributions of firm size, scope, and productivity. Our model explains two puzzles. First, it explains the well-known size-discount puzzle: large firms have lower values of Tobin’s Q than small firms. Second, it explains the globalization-skewness puzzle documented in the empirical part of our paper: a multilateral reduction in trade costs leads to a flattening of the size distribution of firms. In our model, globalization not only affects the distribution of observed productivities but also productivity at the firm level. Download Paper
We present a theory of entrepreneurial entry and exit decisions. Knowing their own managerial talent, entrepreneurs decide which market to enter, where markets differ in size. We obtain a striking sorting result: each entrant in a large market is more efficient than any entrepreneur in a smaller market since competition is endogenously more intense in larger markets. This result continues to hold when entrepreneurs can export their output to other markets, thereby incurring a unit transport cost or tariff. The sorting and price competition effects imply that the number of entrants (and hence product variety) may actually be smaller in larger markets. In the stochastic dynamic extension of the model, we show that the churning rate of entrepreneurs is higher in larger markets Download Paper
We investigate the impact of vertical mergers on upstream firms' ability to sustain tacit collusion in a repeated game. We identify several effects and show that the net effect of vertical integration is to facilitate collusion. Most importantly, vertical mergers facilitate collusion through the operation of an outlets effect: cheating unintegrated firms can no longer profitably sell to the downstream affiliates of their integrated rivals. However, vertical integration also gives rise to an opposing punishment effect: it is typically more difficult to punish an integrated structure, so that integrated firms are able to make more profits in the punishment phase than unintegrated upstream firms. When downstream firms can condition their prices or quantities on upstream firms' contract offers, two additional effects arise, both of which further facilitate upstream collusion. First, an unintegrated upstream firm's deviation profits are reduced by the reaction effect which arises since the downstream unit of the integrated firm will now react aggressively to upstream deviations. Second, an integrated firm's deviation profit is reduced by the lack-of-commitment effect as it cannot commit to its own downstream price when deviating upstream. Download Paper
We develop an assignment theory to analyze the volume and composition of foreign direct investment (FDI). Firms conduct FDI by either engaging in greenfield investment or in cross-border acquisitions. Cross-border acquisitions involve firms trading heterogeneous corporate assets to exploit complementarities, while greenfield FDI involves building a new plant in the foreign market. In equilibrium, greenfield FDI and cross-border acquisitions co-exist, but the composition of FDI between these modes varies with firm and country characteristics. Firms engaging in greenfield investment are systematically more efficient than those engaging in cross-border acquisitions. Furthermore, most FDI takes the form of cross-border acquisitions when factor price differences between countries are small, while greenfield investment plays a more important role for FDI from high-wage into low-wage countries. These results capture important features of the data. Download Paper
In repeated normal-form games, simple penal codes (Abreu 1986, 1988) permit an elegant characterization of the set of subgame-perfect outcomes. We show that the logic of simple penal codes fails in repeated extensive-form games. We provide two examples illustrating that a subgame-perfect outcome may be supported only by a profile with the property that the continuation play after a deviation is tailored not only to the identity of the deviator, but also to the nature of the deviation. Download Paper
We develop a general theoretical framework of trade on a platform on which buyers and sellers interact. The platform may be owned by a single large, or many small independent or vertically integrated intermediaries. We provide a positive and normative analysis of the impact of platform ownership structure on platform size. The strength of network effects is important in the ranking of ownership structures by induced platform size and welfare. While vertical integration may be welfare-enhancing if network effects are weak, monopoly platform ownership is socially preferred if they are strong. These are also the ownership structures likely to emerge. Download Paper
We study rationing as a tool of the monopolist's selling policy when demand is uncertain. Three selling policies are potentially optimal in our environment: uniform pricing, final sales, and introductory offers. Final sales consist in charging a high price initially, but then lowering the price while committing to a total capacity. Consumers with a high valuation may decide to buy at the high price since the endogenous probability of rationing is higher at the lower price. Introductory o.ers consist in selling a limited quantity at a low price initially, and then raising price. Those consumers with high valuations who were rationed initially at the lower price may find it optimal to buy the good at the higher price. We show that the optimal selling policy involves either uniform pricing or final sales. Introductory offers may dominate uniform pricing, but can never be optimal if the monopolist can also use final sales. Download Paper
In this paper we investigate the impact of vertical mergers on upstream firms' ability to sustain collusion. We show in a number of models that the net effect of vertical integration is to facilitate collusion. Several effects arise. When upstream offers are secret, vertical mergers facilitate collusion through the operation of an outlets effect: Cheating unintegrated firms can no longer profitably sell to the downstream affiliates of their integrated rivals. Vertical integration also facilitates collusion through a reaction effect: the vertically integrated firm's 'contract' with its downstream affiliate can be more flexible and thus allows a swifter reaction in punishing defectors. Offsetting these two effects is a possible punishment effect which arises if the integrated structure is able to make more profits in the punishment phase than a disintegrated structure. Download Paper
We present a theory of entrepreneurial entry and exit decisions. Knowing their own managerial talent, entrepreneurs decide which market to enter, where markets differ in size. We obtain a striking sorting result: each entrant in a large market is more efficient than any entrepreneur in a smaller market. The result obtains since competition is endogenously more intense in larger markets. The sorting and price competition effects imply that the number of entrants (and hence product variety) may actually be smaller in larger markets. In the stochastic dynamic extension of the model, we show that the churning rate of entrepreneurs is higher in larger markets. Download Paper
We posit that the value of a manager's human capital depends on the firm's business strategy. The resulting interaction between business strategy and managerial incentives affects the organization of business activities, both the internal organization of the firm and the determination of firm boundaries. We illustrate the impact of this interaction on firm boundaries in a dynamic agency model. There may be disadvantages in merging two firms even when such a merger allows the internalization of externalities between the two firms. Merging, by making unprofitable certain decisions, ncreases the cost of inducing managerial effort. This incentive cost is a natural consequence of the manager's business-strategy-specific human capital. Download Paper
This paper is motivated by the empirical regularity that industries differ greatly in the level of firm turnover, and that entry and exit rates are positively correlated across industries. Our objective is to investigate the effect of sunk costs and, in particular, market size on entry and exit rates, and hence on the age distribution of firms. We analyze a stochastic dynamic model of a monopolistically competitive industry. Each firm's efficiency is assumed to follow a Markov process. We show existence and uniqueness of a stationary equilibrium with simultaneous entry and exit: efficient firms survive while inefficient ones leave the market and are replaced by new entrants. We perform comparative dynamics with respect to the level of sunk costs: entry costs are negatively and fixed production costs positively related to entry and exit rates. A central empirical prediction of the model is that the level of firm turnover is increasing in market size. The intuition is as follows. In larger markets, price-cost margins are smaller since the number of active firms is larger. This implies that the marginal surviving firm has to be more efficient than in smaller markets. Hence, in larger markets, the expected life span of firms is shorter, and the age distribution of firms is first-order stochastically dominated by that in smaller markets. In an extension of the model with time-varying market size, we explore the comovements between market size and entry and exit rates. It is shown that both entry and exit rates tend to rise over time in growing markets. In the empirical part, the prediction on market size and firm turnover is tested on industries where firms compete in well-defined geographical markets of different sizes. Using data on hair salons in Sweden, we show that an increase in market size or fixed costs shifts the age distribution of firms towards younger firms, as predicted by the model. Download Paper
We study rationing as a tool of the monopolist's pricing strategy when demand is uncertain. Three pricing strategies are potentially optimal in our environment: uniform pricing, final sales, and introductory offers. The final sales strategy consists in charging a high price initially, but then lowering the price while committing to a total capacity. Consumers with high valuations to pay may decide to buy at the high price since the endogenous probability of rationing is higher at the lower price. The introductory offers strategy consists in selling a limited quantity at a low price initially, and then raising price. Those consumers with high valuations who were rationed initially at the lower price may find it optimal to buy the good at the higher price. We show that while the introductory offers strategy may dominate uniform pricing, it is never optimal if the monopolist can use the final sales strategy. Download Paper
We present a dynamic agency model in which changes in the structure of a firm affect its value due to altered incentives. There may be disadvantages in merging two firms even when such a merger allows the internalization of externalities between the two firms. Merging, by making unprofitable certain decisions, increases the cost of inducing managers to exert effort. This incentive cost arises as a natural consequence of the manager's firm-specific human capital. Download Paper
We present a dynamic agency model in which changes in the structure of a firm affect its value due to altered incentives. There may be disadvantages in merging two firms even when such a merger allows the internalization of externalities between the two firms. Merging, by making unprofitable certain decisions, increases the cost of inducing managers to exert effort. Download Paper