EDIT: James Russel (@burghdiaspora) hit me up on twitter and said he does not conflate labor mobility and migration, but was trying to show how the two are connected and clarify existing urban economic theory.
In two recent pieces, James Russel and Drew Reed spar over the legitimacy of Jane Jacobs' observations of city life and contemporary claims around the development of walkable urban places as centers of innovation. Russel is aiming, albeit widely, at recent justification for the planning of "innovation districts" and rightly questions the reasoning that supposedly undergird the policy choices of cities and institutions rushing headlong to redevelop whole sections of cities in order to, quite literally, bottle up innovation through a particular physical form. But both commentators fundamentally misunderstand the determinants of urban growth and what Jacobs had to say. As a result, they are boxing with the imperfect translations of Jacobs by, frankly, unqualified hustlers and, in turn, push their own fallacies regarding social science and knowledge formation and misreading two centuries of economic geographic thought.
Reed's response, while energetic, is as unconvincing to me as Russel's broadside on Marshallian agglomerative theory and "Jacobsian spillovers". Reed cannot actually muster the evidence to defend the claims others make of Jacobs' work (something neither Russel or Reed actually explore is what Jacobs actually wrote, but that's another issue) and, instead takes offense at Russel's use of the term "pseudoscience" to describe the sloppy application of Jacobs' writings and basically calls Russel a hurtful bully for attacking a woman who helped to, supposedly, resuscitate the idea of cities as positive places to be. Neither response is particularly profound, but the former deserves a bit of exploration before diving into more important questions of urban growth and agglomeration.
Reed takes offense at the application of Jacobs' work as pseudoscience and attempts to sidestep the critique by saying that social science can never be as certain as the natural or life sciences and it is impossible to determine what amount of evidence is actually necessary to test a social scientific claim. This argument, essentially, says that any social scientific claim can basically be taken as legitimate because the causal mechanisms are always messy and testing is nigh impossible. Such a position is profoundly dangerous because it destroys any meaningful reason for the existence of social science if social science is to actually clarify the whys and how of social phenomena. While social phenomena are rarely mechanistic and regular, the best social science seeks to clarify and sketch out particular causal mechanisms and the conditions by which those mechanisms arise or work themselves out (admittedly, I am drawing from the realist school here, in particular, Andrew Sayer).
While this is not the space to dive deeply into questions of the varied ontologies and epistemological approaches of social science, the schools that have trained me are quite clear that social science allows for the testing of claims, the weighing of evidence, the delineation of causal mechanisms etc...that make it possible to definitively reject certain conceptions and theories. The abandonment (though it is still applied in some areas) of early Chicago School human ecological notions of the city are no longer considered valid, though they are making a comeback through the uncritical application of ecological metaphors from some commentators. So Reed's claim that we cannot come up with a way to garner enough evidence to test the claims made by certain innovation proponents holds little weight. This does not that Russel's waving of one paper discussing labor mobility between firms is enough evidence to either convince us to move away from the Jacobs-inspired commentators or accept his notion, but it is certainly one piece of evidence that we should be considering.
On to Russel's claims concerning growth. If Russel were merely critiquing the application of Jacobs' observations about walkable places and innovation, then I do not think there would be any serious issue. Even if you are a die-hard Jacobs acolyte, such crude applications and insistence of the physical determinism of certain physical arrangements of buildings and infrastructure and economic development should offend anyone who thinks deeply on cities and economics. But Russel seeks to extend the critique by attacking the notion of Marshallian industrial districts, Porter's cluster theory, and the general idea of external economies and agglomerative forces, in general. While cute, it is a step too far and exposes some confusion on his part, even within his own arguments.
The problem with Russel's view rests on a few parts, but due to space limitations I will focus mainly on the question of scale, a particularly fruitful area, I think, as Russel is a geographer. The problem is that Russel smashes all scales together, a cardinal sin in geography where scale and space are central to how the field understands disparate social, political, economic, and cultural phenomena.
Russel thinks he has hit upon a gap in the understanding of economic and urban geography, but it is a misreading of the literature and more progressive economic development policy. It becomes clear when Russel conflates migration and labor mobility a la the paper he cites on labor movement among firms and its ties to innovation. Because Russel does not distinguish between scales he combines migration, both inter-regional and international, and labor mobility between firms. Specifically, a region could have extensive mobility among firms without necessarily relying on external migration and still innovate or, more likely, such innovation would then encourage greater growth and migration from those looking to take advantage either through entrepreneurial concerns or working for growing firms. Such a model encompasses both the importance people, from individual entrepreneurs to common labor pools, while recognizing the different scales and times at which these operations can occur. The essential unstated aspect of this firm mobility still rests on the co-location of similar firms, the pooling of a labor supply, and the existence of a set of supporting firms. In other words, the same essential aspects that Marshall first pointed out and that economic geographers have elaborated upon since in different ways.
This one particular illustration is not novel, by any means. It is, actually, a fairly common way that economic geographers, planners, and economists actually conceive of urbanization growth and external benefits of co-location. While Marshallian industrial districts may be too restrictive to understand the rise of the polycentric urban form that characterizes the spatial organization of advanced economies in later capitalism, it is also equally simplistic to dismiss the existence of agglomeration and urbanization economies that rest upon spatial propinquity. This does not give a magical power to place, per se, but the "people aspects" that Russel points to as essential to innovation still must occur somewhere and it is that question of where that remains that Russel does not contend with. Now recognizing co-location and propinquity as important to economic development and innovation does NOT mean that innovation only occurs in specific areas or with specific spatial configurations. But in seeking how to sketch out the causal mechanisms and the conditions necessary for that innovation to occur it is nonsensical to throw out over two centuries of economic and geographical thought that have shown quite clearly that agglomeration and urbanization economies exist, and that urban-regional areas are hotbeds for innovation precisely due to the combination of a constant influx of people, concentration of similar firms, and ancillary firms that provide essential support services from legal and financial services to equipment leasing.
The question, then, is not one of people versus place but of the unique combinations of people and the organization of space that results in different places. The existence of true megapolitan and regional agglomerative economies show the lie of the "innovation district" boosters that insist that certain innovations are so neatly geographically circumscribed or that they can increase innovation through the "accidental bumping" of people in a place. A kind of Brownian motion theory of industrial development that does, in defense of Russel, rest firmly in the realm of pseudo-scientific reasoning.
I would like to end by actually coming to the defense of Jacobs and something that both Russel and Drew did not do in their posts-engage with what Jacobs actually wrote. Commentators using Jacobs to justify "innovation districts" or the economic impacts of walkable places actually fundamentally misread what Jacobs actually wrote on the economy of cities (no, really, she has a book called "The Economy of Cities") and nowhere in her descriptions and theorizing of how cities grow and how cities operate economically does she say anything as facile as "walkable" places beget innovation. In fact, Jacobs builds on scholars like Chinitz(a truly classic paper in the field), and other mid-century economists and geographers, to give an elegant set of descriptions on how entrepreneurship, increasing industrial specialization, increasingly sophisticated divisions of labor, and local institutional variations seed urban economic growth. Her description of urban economic development as the creation of "new work", an explicit nod to innovation both of the disruptive and non-disruptive kind, is still an elegant way to describe the mechanics of urban economic growth.
The question of how to encourage innovation is one that is at the forefront of policymakers minds and we certainly need a much better understanding of the actual work that's been done on the topic. "Innovation districts", as they stand, will likely be relatively expensive boondoggles that were good excuses for cities to blight and redevelop poor neighborhoods near universities, but will likely not have the kind of massive impact boosters promise. But their willful misreading of Jacobs and ignorance of the last forty years of economic geography is not at all an indictment of the theories of agglomeration and urbanization economies nor of Jacobs' own work. We can debate just how exactly "spillover" benefits operate (is it some magical property of space or labor mobility?) but the fact that innovation, the kind of innovation people write so many books and articles about, happens repeatedly in similar places means that the question is not whether space matters, clearly it does, but how does it matter?