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such as the U.S. manufacturing belt, would find their advantage reinforced as more firms were induced
to move there. Whether the possibility of multiple equilibria was really appreciated at first is less clear.
A case in point was the pioneering modeling effort by Lowry (1964). Lowry produced something that
was remarkably ahead of its time: a calibrated numerical model of land use within a city (Pittsburgh) in
which many location decisions were endogenous, and in which implicit increasing returns implied
multiple equilibria. Lowry's model was not based on maximizing behavior it could not have been, given
the state of the modeling art at that time. Instead, he imposed a set of plausible, ad hoc rules. Location
decisions by firms, in particular, were based largely on market potential.
This was, to repeat, a remarkable and pioneering effort. And yet there are signs that Lowry himself did
not fully understand what he was up to. In particular, there is a giveaway remark in which he says that it
is crucial to solve the equations in the right order if they are solved in the wrong order, they give
different answers! In other words, he regarded the multiple equilibria in his model as a nuisance, not as
an insight into the process of spatial development.
But if the geographers who worked with market potential may not have been entirely clear-minded
about the possibility of circularity, there were other geographers who were very aware of that
possibility, for a very good reason: they were sitting at the feet of the creators of high development
theory.
Consider the story of multiple equilibria I have just told, in which firms locate where markets are large,
but markets are large where firms locate. Isn't this essentially the same
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