This paper studies the estimation of the cost of non-sequential search. We provide a new method based on semi-nonparametric (SNP) estimation that allows us to pool price data from different consumer markets with the same underlying search cost distribution but different valuations or selling costs. We show that pooling data from different markets increases the number of estimated critical search cost cutoffs at all quantiles of the search cost distribution, which increases the precision of the estimates. A Monte Carlo study shows that the method works well in small samples. We apply our method to a data set of online prices for memory chips and find that the search cost density is essentially bimodal such that a large fraction of consumers searches very little, while a smaller fraction of consumers samples a relatively large number of stores.

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This paper studies mergers in markets where firms invest in a portfolio of research projects of different profitability and social value. The portfolio nature of the investment problem brings about novel insights on the external effects of firms' investments. The investment of a firm in one project imposes a negative business-stealing externality on the rival firms because it lowers the probability they win the innovation contest for that project; however, the investment of a firm in one project also exerts a positive business-giving externality on the rival firms because it increases the likelihood they win the contest for the alternative project. Merging firms internalize these positive and negative externalities they impose on each other. We show that when the project that is relatively more profitable for the firms is also the more appropriable, then a merger increases consumer welfare by reducing investment in the most profitable project and increasing investment in the alternative (less profitable) project. For the case of linear demand and constant marginal costs, the portfolio effect of mergers makes them consumer welfare improving. With constant elasticity of demand and constant marginal costs, a merger increases consumer welfare if the more profitable project corresponds to the market with the higher elasticity of demand. The portfolio effect of mergers may dominate the usual market power effects of mergers.