In the period since the end of World War II, the Japanese economic achievement has been of prodigious proportions. During this period, its growth rate—an average of almost 10% in GNP per year—has been the highest in the world. Japan has become the third-ranking industrial nation and its world standing, in terms of per capita GNP, has risen from fortieth in the early 1950s to twelfth at the present time. Growth so sweeping and rapid inevitably has brought a multitude of changes, not least in the composition of total output. At a highly accelerated rate, industries have declined, others have blossomed, new industries have appeared, and the importance of various sectors of the economy has changed. Amidst the continuing adjustments and readjustments, it is of interest to consider the nature of the impact on Japanese industrial organization. More specifically, what has been the effect on economic concentration and monopoly in Japan?