Diversification, Ricardian Rents, and Tobin's q
提出，选择广泛多元化的企业预期平均租金最低，并用托宾q衡量租金进行了实证检验，结果支持该理论。
According to prevailing theory, firms diversify in response to excess capacity of factors that are subject to market failure. By probing into the heterogeneity of these factors, we develop the corollary that firms that elect to diversify most widely should expect the lowest average rents. An empirical test, with Tobin's q as the measure of rents, is consistent with this theory.