The notion of complementarity is fundamental to economics, as reflected in the large and growing number of studies that invoke alternate conceptions of this idea. Though complementarity has been studied for many years, its connection with theory of supermodularity is far more recent. Taking advantage of these techniques, the first three chapters of this dissertation study aspects of interest in network markets; endogenous information acquisition; and some insights into the comparison of player's equilibrium strategies. The last chapter applies this methodology to econometric identification.Chapter one provides a thorough analysis of oligopolistic markets with positive demand-side network externalities and perfect compatibility. With a general complementarity structure on the model primitives allowing for products with low or high stand-alone values, a nontrivial fulfilled-expectations equilibrium exists. We formalize the concept of industry viability, investigate its determinants, and show that viability is always enhanced by having more firms in the market and/or by technological progress.The second chapter studies covert information acquisition in common value Bayesian games of strategic complementarities. Using the supermodular stochastic order to arrange the structures of information increasingly in terms of preferences, we provide novel, easily interpretable conditions under which the value of information is globally convex, and study the implications in terms of the equilibrium configuration. Our analysis also enlightens the effect of information on players' behavior.Chapter three proposes a simple approach to compare players' equilibrium choices in asymmetric games with strategic complementarities. We offer three applications of our idea to industrial organization and behavioral economics.The last chapter studies (nonparametric) partial identification of treatment response with social interactions. It imposes economically driven monotone conditions to the primitives of the model, i.e., the structural equations, and shows that they imply shape restrictions on the distribution of potential outcomes by means of monotone comparative statics. We propose precise conditions that validate counterfactual predictions in models with multiple equilibria. Under three sets of assumptions, we identify sharp distributional bounds (in terms of stochastic dominance) on the potential outcomes given observable data. We illustrate our results by studying the effect of police per-capita on crime rates in New York state.

Nesta tese, estudamos um arcabouço, introduzido por Frank, que denominamos de sistemas generalizados de núcleos. Provamos teoremas sobre empacotamentos de certos objetos combinatórios neste arcabouço, tanto para o caso inteiro quanto para o fracionário. Estes teoremas, em particular, implicam em uma melhora nos limitantes superiores de Schrijver, para o empacotamento de ramificações, e de Gabow e Manu, para o empacotamento de arborescências. Além disso, também provamos que o problema de minimização num poliedro relacionado pode ser resolvido em tempo polinomial, dado um oráculo de separação. / We study a framework, which we call a generalized kernel system, introduced by Frank. We prove some integral and fractional packing theorems on this framework which, in particular, imply an improvement on the best upper bounds currently known, one due to Schrijver, for packing branchings from a given root-sets, and another, due to Gabow and Manu, for packing spanning arborescences from a given root. We also establish the polynomial time complexity, modulo a separation oracle, of a related minimization problem involving a polyhedron derived from this framework.

Nesta tese, estudamos um arcabouço, introduzido por Frank, que denominamos de sistemas generalizados de núcleos. Provamos teoremas sobre empacotamentos de certos objetos combinatórios neste arcabouço, tanto para o caso inteiro quanto para o fracionário. Estes teoremas, em particular, implicam em uma melhora nos limitantes superiores de Schrijver, para o empacotamento de ramificações, e de Gabow e Manu, para o empacotamento de arborescências. Além disso, também provamos que o problema de minimização num poliedro relacionado pode ser resolvido em tempo polinomial, dado um oráculo de separação. / We study a framework, which we call a generalized kernel system, introduced by Frank. We prove some integral and fractional packing theorems on this framework which, in particular, imply an improvement on the best upper bounds currently known, one due to Schrijver, for packing branchings from a given root-sets, and another, due to Gabow and Manu, for packing spanning arborescences from a given root. We also establish the polynomial time complexity, modulo a separation oracle, of a related minimization problem involving a polyhedron derived from this framework.

We consider two game-theoretic settings to determine the optimal values of an issuer's interchange fee rate, an acquirer's merchant discount rate, and a merchant's retail prices for multiple products in a credit card network. In the first setting, we investigate a two-stage game problem in which the issuer and the acquirer first negotiate the interchange fee rate, and the acquirer and the retailer then determine their merchant discount rate and retail prices, respectively. In the second setting, motivated by the recent U.S. bill "H.R. 2695," we develop a three-player cooperative game in which the issuer, the acquirer, and the merchant form a grand coalition and bargain over the interchange fee rate and the merchant discount rate. Following the cooperative game, the retailer makes its retail pricing decisions. We derive both the Shapley value- and the nucleolus-characterized unique rates for the grand coalition. Comparing the two game settings, we show that the participation of the merchant in the negotiation process can result in the reduction of both rates. Moreover, the stability of the grand coalition in the cooperative game setting may require that the merchant should delegate the credit card business only to the issuer and the acquirer with sufficiently low operation costs. We also find that the large, highly-specialized merchants and banks are more likely to join the cooperative negotiation whereas the small firms may prefer the two-stage game setting. Our numerical experiments demonstrate that the acquirer's and the issuer's unit operation costs more significantly impact both rates in the cooperative game setting than in the two-stage game setting.

本研究旨在探討研發取得策略，情境因子，研發人力資本，與公司績效之間的關聯性。藉由理論模型的推導與實務訪談研發中心主管來發展假說，進而以混合資料模型(pooled data models)與橫斷面資料模型來進行實證分析。主要結果為：當公司的研發多樣化程度較高，專利權數目較少，公司較可能採取內外部研發並進策略(R&D hybrid strategy)，而非完全內部研發策略(make strategy)。最重要地，過度/低度的外部研發取得(under-/over-external R&D sourcing)對於公司績效有負/正向影響。相較於會計績效，此效果對市場績效的影響尤其顯著。同時，研發取得策略對於公司績效的影響，取決於公司的研發人力資本。相較於採取完全內部研發策略的公司，為了吸收外來的異質技術，採取內外部研發並進策略的公司較可能聘任不同研發種類的研發人員；而如此的研發取得策略與研發人力資本契合將進而改善會計與市場績效。本研究的發現與交易成本理論與supermodular理論一致。如同預期，相較於橫斷面資料模型，本研究的實證分析在混合資料模型較為顯著。 / The association between performance and R&D sourcing strategy in relation to contextual variables and R&D human capital is determined by the analytical model coupled with field interviews with directors or managers in R&D centers. Capitalizing on a unique database of the 2001-2003 Taiwan Industry R&D Investment Survey containing more detailed information available on the R&D activities to verify this association, the researcher tests the empirical results by cross-sectional and pooled data models. The findings are that an innovating firm will prefer to implement the R&D hybrid strategy when the higher degrees of R&D diversity and fewer counts of patents are exhibited. Perhaps most importantly, this study shows compelling evidence that over-/under-external R&D sourcing affects negatively/positively a firm’s performance. This effect is more significant in the market-based performance (Tobin’s q and average two-year Tobin’s q) than accounting-based performance (ROS and ROA). Moreover, the associations between R&D sourcing strategy and a firm’s performance are contingent on the use of R&D human capital. Innovative firms with the R&D hybrid/make strategy are more/less prone to employee diverse types of R&D experts to absorb the coming external knowledge, and such alignment between R&D sourcing strategy and R&D human capital thus improves both accounting- and market-based performance. The results are consistent with both transaction cost paradigms that discriminating alignment of transactions with strategy leads to more efficient outcomes, and the supermodularity model that a firm’s performance is a function of coherent alignment between strategy and structural elements of an organization. As predicted, these effects are noticeable and more pronounced in the pooled data model than in the cross-sectional design.