 'The Dirichlet', as it became known, accounts for a number of empirical generalisations, including Double Jeopardy, the Duplication of Purchase law, and Natural Monopoly.It has been shown to hold over different product categories, countries, time, and for both subscription and repertoire repeat-purchase markets.It has been described as one of the most famous empirical generalisations in marketing, along with the Bass model of diffusion of innovation.