# 19.01 Technological Diversification of U.S. Cities during the Great Historical Crises

Mathieu P.A. Steijn and Pierre-Alexandre Balland and Ron Boschma and David L. Rigby

 

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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, and whether the impact differs between specialised and diverse regions. This paper offers systematic evidence on the effects of three of the largest crises in U.S. history (the Long Depression 1873-1879, the Great Depression 1929-1934, and the Oil Crisis 1973-1975) on the development of new technological capabilities within U.S. metropolitan areas. We find that crises reduce the pace of diversification in cities and that they narrow the scope of diversification to more closely related activities. We also find that more diverse cities outperform more specialised cities in diversifying during times of crisis but more diverse cities do not have a stronger focus on less related diversification during these unsettled times.

# 13.16 Relatedness and Technological Change in Cities: The rise and fall of technological knowledge in U.S. metropolitan areas from 1981 to 2010

Ron Boschma, Pierre-Alexandre Balland, Dieter Franz Kogler

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This paper investigates by means of USPTO patent data whether technological relatedness was a crucial driving force behind technological change in 366 U.S. cities from 1981 to 2010. Based on a three-way fixed effects model, we find that the entry probability of a new technology in a city increases by 30 percent if the level of relatedness with existing technologies in the city increases by 10 percent, while the exit probability of an existing technology decreases by 8 percent.