Relative Market Share, Leadership and Competition in Concentrated Banking Markets

For many years IO economists devoted attention to the size distributions’ of firms in a given industry. Most studies showed that the size distribution of firms in oligopolistic markets is highly skewed. There are many small firms and a few large firms. There is also a consensus that relative market shares are important and that large firms are, in general, more profitable and durable than small firms. Relative size is also important as a determinant of the structure of the industry. The concept is also central in strategic analysis of business firms and in the formulation of government (regulatory) policy. In this paper we propose to use an empirical measure of market leadership. The measure relies on the assumption that the degree of competition critically depends on how dominant the leading firm is in a given industry. The measure also takes into account the number of “significant” competitors in the market and how close they are to the leading firm in terms of size. The measure is simple to use and easy to interpret. It also yields a critical value that facilitates comparisons between different markets.