Surviving in agglomerations: Plant evolution and the changing benefits of the local environment

Cities vary with regard to the characteristics of their economic life. A formal model by Duranton and Puga (2001) suggests a division of labour between diversified and specialized cities. Diversified cities (the “nursery cities”) provide a fertile environment for search and innovation. Specialized cities, by contrast, are better equipped to facilitate mass-production. In essence, this spurs firms to re-locate as they mature from the exploratory set-up stage to mass-production. In this article, we empirically test the assumptions behind this model by means of survival analysis using Swedish plant level data of over 11 000 plants. More specifically, we investigate the effects of local specialization and local diversity on plant survival at different ages of a plant and for different size categories of plants. Not all types of local diversity will be of value to a plant. Rather, we expect plants to benefit especially from local diversity in related industries. In a similar vein, cities with a large concentration of a broad range of activities in related trades may confer larger benefits than cities with a narrow specialization in the plant’s own industry. To quantify the degree of relatedness between industries, we use a new measure, Revealed Relatedness. This serves to identify technological relatedness by measuring economies of scope as implied by the structure of production portfolios of plants. The findings suggest that regional characteristics strongly influence the chances of a plant to survive. In general, the hypothesized specialization effects are only found when we look at related specialization. Large plants at high stages of maturity form the only exception to this. However, diversity effects are only visible when we take all local diversity into account, not just diversity in related industries. Moreover, it is only young firms that benefit from regional diversity. This indicates that the “nursery city” metaphor holds as much for small, prototype plants as for large mass-production plants.