Abstract: Why didn’t the Japanese miracle take place before World War II? The culprit we identify is a barrier that kept prewar agricultural employment constant. Using a standard neoclassical two-sector growth model, we show that the barrier-induced sectoral distortion and an ensuring lack of capital accumulation account well for the depressed output level. Without the barrier, Japan’s prewar GNP per worker would have been at least about a half of that of the United States, not about a third as in the data. The labor barrier existed because, we argue, the prewar patriarchy forced the son designated as heir to stay in agriculture.