Next year, Paris will swallow most of its suburbs into an enlarged city government in an attempt to correct inequities that have trapped poor and immigrant Parisians in huge suburban housing complexes where unemployment is high and quality of life low. Paris’ action comes on the heels of similar annexations and consolidations in cities from Toronto to Louisville over the last 20 to 30 years. ... All of this ferment points to one big unanswered question: What is the right form for a city’s government?

“I think another way of putting the question is, ‘What’s the optimal size for a metropolis?’” says Bruce Katz, vice president and co-director of the Brookings Institution’s Metropolitan Policy Program. “Even before we get to the government question, there’s a debate about how big you need to be to compete globally.”

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But even in a federal metropolis or a regional revenue-sharing arrangement, the question of optimal size remains, and here Katz says there is such a thing as governments that are too small. Into that category fall many of the 91 municipalities where St. Louis County’s one million citizens reside. “At some point, we just have to bite the bullet here, and that’s what Denmark had to do,” he says. “Many London boroughs are quite large.”

The one thing that Katz thinks is certain: Change will come, because it must. New balances must be struck between local autonomy and democratic participation and metropolitan economic organization, and the process of achieving that new balance will be messy. “We’re trying to achieve different but complementary goals around efficiency and inclusion,” he says. “I hope the next two decades are a period of experimentation in the United States.”