In his Preface to Urban Economics, Wilbur Thompson describes, in terms of industry mix, a system of urban area tradeoffs among income level, income equality, and income stability [9, Chapter 2]. For example, Flint, Michigan, will have a relatively high level of income because of its relatively large fraction of employment in higher paying durable manufacturing industries and a relatively more equal distribution of earnings because of the strong union influence in durable manufacturing industries; but precisely because of the dominance of durable goods industries, it will be subject to a relatively high degree of cyclical instability. The issues of urban income level and urban income equality have received an increasing amount of attention in the still new literature of urban economics, but the stability question-particularly as it relates to diversity in industrial structure-has been largely ignored. The basic purpose of this research is to make interurban comparisons of the industrial diversification dimension of local stability.