The apple doesn't fall far from the tree. Long-distance migration is remarkable, the exception to the rule (an actual "law" of migration). Why are large, dense cities typically centers of innovation and creativity? Most migrants only proceed a short distance, and toward centers of absorption:
Labor as a primary conduit for IT spillovers has implications for their geographic scope. More than other mechanisms, labor mobility tends to be local, so the economic effects of IT spillovers are likely to be stronger over smaller distances. This assertion is consistent with an extensive and influential literature on the role of geography for R&D spillovers, where scholars have found that R&D spillovers tend to be stronger over smaller distances (Jaffe, Trajtenberg, and Henderson 1993; Audretsch and Feldman 1996). Higher R&D spillovers in some regions are due in part to the importance of employee mobility for facilitating knowledge transfer (Audretsch and Stephan 1996; Almeida and Kogut 1999). The importance of labor mobility for the transmission of IT skills suggests that geography will also be important for understanding IT spillovers, and this argument is supported by the well-documented importance of labor mobility within high-tech clusters for economic growth (Saxenian 1996; Bresnahan and Gambardella 2004), which emphasizes the importance of location for high-tech innovation, and argues that the flow of technical skills among firms is a principal driver of the rapid innovation rates observed for firms in these cities.
I left in the citations from the paper, titled "Job Hopping, Information Technology Spillovers, and Productivity Growth." The part of the passage I highlighted explains how this research fits within the dominant scholarly narrative. Because most migration (i.e. "labor mobility") covers a short distance, spillovers appear to agglomerate in large, dense cities. But talent migration as a primary conduit of IT spillovers doesn't preclude long-distance spillovers, as noted by AnnaLee Saxenian in "Local and Global Networks of Immigrant Professionals in Silicon Valley" (PDF).
That the findings are consistent with the academic literature on urban economic theory is a good thing. The extensively observed holds true. But the usual explanation for the extensively observed takes on a lot of water. Without migration, there is no innovation.
If not innovation districts, then how should we spur innovation and creativity? To the footnotes!
The economic importance of this type of employee mobility in the IT sector is suggested by recent press covering the Department of Justice investigation of collusive non-poaching agreements in several prominent technology firms (Catan & Kendall, 2010), as well as in coverage of the difficulties faced by large tech firms in slowing the defection of employees to competitors (Efrati & Morrison, 2010).
Footnote #1 expounds upon this sentence: "This is consistent with patterns observed for the spread of other general-purpose technologies—for example, economists have hypothesized that skilled engineers were important for the diffusion of know-how required for the installation of the electric dynamo in US factories (David, 1990)." Academic literature cavorts with current events.
We don't need innovation districts or greater density. We should 86 non-compete agreements. We need more migration.