If mayors ruled the world

LONDON, ENGLAND - APRIL 30:  Boris Johnson, the Mayor of London, campaigns in Camden for the Conservative party on April 30, 2010 in London, England. Politicians are continuing to canvass for support with less than one week to go before the general election on May 6, 2010.  (Photo by Oli Scarff/Getty Images)

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    If mayors ruled the world

CNN's Hala Gorani, in for Christiane Amanpour, speaks with Benjamin Barber about the innovation of cities.