Abstract
This paper examines statistically the dispersion of corporate technological leadership in sectors of rapid development historically. The evidence provided is based on the US patenting of 284 of the largest American and European industrial firms since 1890. It is shown that the diffusion of innovation to followers that are 'catching up' in a sector of activity is associated with an especially rapid rate of overall development in that field; that is, the rate of catching up is positively related to the rate of advance. However, during such phases of fast growth leaders tend to preserve at least some elements of their leading position. It is only over longer historical periods that the actual composition of leadership in a sector tends to shift more significantly.