The Size of Firms and R&D Investment
构建了一个行业均衡模型，其中消费者转换成本赋予企业对老客户的市场力量，模型预测大企业利润更高、研发投入更多、平均定价更低，且利润随时间正相关，这些特征与美国制造业和零售业的实证规律一致。
We construct an industry‐equilibrium model in which it is costly for consumers who have previously purchased from one firm to switch to competitors. This gives firms a certain degree of market power over their established customers. The equilibria we identify under these conditions have the following properties: (1) there is a nontrivial size distribution of firms, although firms are intrinsically identical, (2) larger firms make higher profits, (3) larger firms spend more on R&D, (4) larger firms charge (on average) lower prices, and (5) profits are positively correlated over time. These properties match empirical regularities concerning the manufacturing and retail sectors in the U.S. economy.