The economic indicators that surround us are familiar, as are the criticisms they attract. The consumer prices index doesn’t fully capture the boon of new products; unemployment figures do not count workers who have given up the job hunt in despair; gross domestic product (GDP) includes bad things if they have a market price, and excludes good things if they don’t.

But there is one fundamental flaw in all these statistics that is rarely discussed: they are almost always applied to countries. It is not impossible to find educated guesses about the GDP of Cambridge, or the inflation rate in Mumbai, and there is nothing conceptually troubling about trying to calculate either. Yet most economic statistics describe the nation state.

This is odd, because the nation state is a political unit, not an economic one. Policy does influence the economy, of course — national authorities can impose a common interest rate, tax rates and regulations. But, as the unorthodox thinker and writer Jane Jacobs used to argue, the natural unit of macroeconomic analysis is not a nation state at all. It is a city and its surrounding region.