In this month's episode, Andrew talks to Dr Thomas Kemeny, co-author of the book The Rise and Fall of Urban Economies, about the insights to be gained from comparing the diverging economies of Los Angeles and the Bay Area in California. In the 1970s, the two city regions were performing at a similar level, but since then the latter has become home to one of the most productive clusters in the world (Silicon Valley), while the former has not kept up with other cities in the United States. Kemeny discusses how the book tries to explain this divergence, making use of several disciplines and sources of evidence. The conversation touches on the changing fortunes of LA's film industry, whether the Bay Area will remain at the 'cutting edge' of new ideas, and the role of networks in encouraging innovation. It ends with a discussion of the importance of cities understanding their place in the global economy, and how our understanding of economic development has changed in recent years.