Geography Reference
In-Depth Information
What Jacobs describes in her topics are essentially large metropolitan
centres, but her argument on diversity spurring knowledge transfer and
diffusion, and therefore economic growth, has been applied to geographi-
cal scales other than the urban area.
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There are obviously differences
between urbanization and diversification economies, as the former often
imply the latter, but the reverse does not generally hold. For example,
both London and the region of Baden Wurttemberg are considered to
be highly industrially diversified, but the forces of spatial agglomeration
and the mechanisms for spillovers follow different channels. Moreover,
the issue is further complicated by the fact that while there is evidence to
suggest that the link between innovation and cities can be strong, particu-
larly with respect to certain sectors (e.g., Acs 2002; Duranton and Puga
2005), there is also much support to the fact that cities do not always seem
to be innovation cores (Shearmur 2011), nor does innovation necessarily
concentrate on cities (e.g., Simmie and Sennet 1999).
Some empirical studies have advocated dynamic agglomeration exter-
nalities across industries as a primary source for regional economic
growth (e.g., Glaeser et al. 1992; Feldman and Audretsch 1999; Paci and
Usai 2009). Some others have found dynamic agglomeration externali-
ties to be particularly strong within the same sector, supporting the view
of localization economies and intra-industry spillovers as a major engine
for localized growth (e.g., Henderson et al. 1995; Forni and Paba 2001).
Other scholars have obtained mixed results for different sectors within the
same region, with sectoral diversity having positive (e.g., Combes 2000, for
services) as well as negative (e.g., Combes 2000, and Blien and Suedekum
2005, for manufacturing) effects on growth, also in dependence on the
industry life cycle (e.g., Audretsch and Feldman 1996). Recent contribu-
tions have shown that the results on the supposedly causal connection
structure-performance at the regional level are actually highly dependent
on methodological choices, varying sensitively to the adoption of different
geographical units of analysis, estimation methods, variable specification,
sectoral aggregation, etc. (e.g., Coombs 2000; Van Oort 2004; Mameli
2007; Mameli et al. 2008).
Yet, what emerges in the actual world is the coexistence of different
regional specialization patterns, any of which may lead to success or failure
in the competitive struggle. To understand the links between diversity and
growth it is therefore necessary to go more in to depth on the meaning of
'regional diversity'. As recognized by Jacobs herself, knowledge spills over
effectively only when complementarities exist among industries in terms
of shared competencies and capabilities. Such complementarities are cap-
tured by the notion of
related variety
(Boschma 2004, 2005; Frenken et al.
2007; Boschma et al. 2009; Boschma and Iammarino 2009). To understand
