Technological diversification of U.S. cities during the great historical crises
研究了美国历史上三次大萧条（1873-1879、1929-1934、1973-1975）对城市技术多样化的影响，发现危机减缓了多样化速度并缩小了范围，且这种模式会阻碍就业增长。
Abstract Regional resilience is high on the scientific and policy agenda. An essential feature of resilience is diversifying into new activities but little is known about whether major economic crises accelerate or decelerate regional diversification. This article shows how crises impact the development of new technological capabilities within U.S. metropolitan areas by examining three of the largest downturns in U.S. history, the Long Depression (1873–1879), the Great Depression (1929–1934) and the 1970s recession (1973–1975). We find that crises (i) reduce the pace of diversification in cities and (ii) narrow the scope of diversification to more closely related activities. This pattern seems general as it also holds for smaller, local crises. Evidence is presented that this general pattern of technological diversification strongly hampers employment growth. Additionally, we find that diverse cities generally diversify more strongly during times of crisis.