Relatedness, industrial branching and technological cohesion in US metropolitan areas, Regional Studies. Work by evolutionary economic geographers on the role of industry relatedness for regional economic development is extended into a number of methodological and empirical directions. First, relatedness is measured as the intensity of inputoutput linkages between industries. Second, this measure is employed to examine industry evolution in 360 US metropolitan areas. Third, an employment-weighted measure of metropolitan technological cohesion is developed. The results confirm that technological relatedness is positively related to metropolitan industry portfolio membership and industry entry and negatively related to industry exit. The decomposition of technological cohesion indicates that the selection of related incumbent industries complements industry entry and exit as the main drivers of change in metropolitan technological cohesion.