A Generalized Index of Diversification: Trends in U.S. Manufacturing
定义了一个适用于制造企业和工厂的多样化指数，该指数综合考虑产品数量、分布和异质性，并利用1963-1982年美国制造业普查数据计算了各企业和工厂的指数值，发现企业多样化上升而工厂多样化下降。
An index of diversification suitable for manufacturing plants and firms is defined as a function of product number, distribution, and dissimilarity. A novel feature of the index is its continuous treatment of product heterogeneity. Using "Census of Manufactures" data files, the index is constructed for each establishment and each enterprise surveyed in the 1963-1982 censuses. Results are reported at the 2-digit SIC level. While quantifying the upward trend in enterprise diversification, the index reveals an ubiquitous and persistent decline in establishment diversification. Over time, enterprises are shifting toward a more diverse portfolio of increasingly homogeneous plants. Technical economies of scope appear to play little role in explaining the measured increase in enterprise diversification. Copyright 1991 by MIT Press.