Evolutionary theories of economic development stress the role of variety as both a determinant and a result of growth. In this paper we develop a measure of variety, based on Weitzman’s maximum likelihood procedure. This measure is based on the distance between products, and indicates the degree of differentiation of a product population.
Bernard Bourgeois, Phuong Nguyen, Pier-Paolo Saviotti, Michel Trommetter. Variety and the evolution of refinery processing. Industrial and Corporate Change, Oxford University Press (OUP), 2005, 14 (3), p. 469-500
see also Entropy