I found a really interesting article about knowledge spillovers and their impact on cities, by a guy who is with the Philadelphia Fed -- see Carlino - Knowledge Spillovers. Worth a read!
It's interesting because it also connects with work by Jacobs, and helps to flesh out the economic argument for public space. See also Jacobs Spillovers as a Model of Urban Dynamics.
This paper compares "Jacobs Spillovers" (knowledge spillovers between different industries) with so-called MAR Spillovers (knowledge spillovers within the same industry). The author uses the approach also taken by my ASU/Santa Fe colleague Jose Lobo, among others -- including Emily Talen's husband Luc Anselin -- which uses patents as a proxy measurement for knowledge spillovers. (Somewhat limited as not all creative fields and not all companies tend to use patents and they tend to concentrate in tech fields with bigger companies - but it's a helpful proxy for what is otherwise hard to measure, as he notes.)
Etc etc etc