Between 1990 and 2010 the rate of economic convergence across American states slowed to less than half what it had been between 1880 and 1980. It has since fallen close to zero. Rich cities started pulling away from less well-off counterparts (see chart 1). According to the Brookings Institution, a think-tank, in the decade to 2015 productivity growth in American metropolitan areas was highest in the top 10% and the bottom 20% (where, by definition, the baseline was low). Struggling middle-income cities like Scranton fell further behind. A recent report by the OECD found that, in its mostly-rich members, the average productivity gap between the most productive 10% of regions and the bottom 75% widened by nearly 60% over the past 20 years.