Inequality is greater in big cities than in rural areas, according to recent research from Brookings, and inequality is growing in Minneapolis.

Brookings calculated the ratio of the 95th percentile in income to the 20th percentile, and found that the national average is 9.1 -- that is, people at the 95th percentile get 9.1 times as much income as people at the 20th percentile. It's $191,770 versus $20,968.

The ratio – or the gap between the 95th and the 20th percentiles -- is larger in big cities, at 10.8.

Minneapolis is pretty much average for a big city – at 10.9 – and is far less unequal than several other large cities, such as Atlanta, San Francisco and Miami.

But even in Minneapolis, inequality grew from 2007 to 2012. Thanks to larger proportional declines in income for people in the 20th percentile than for the richest people in Minneapolis, the ratio rose 0.4 points.

The research showing higher inequality in big cities pairs nicely with the recent Equality of Opportunity project, which shows that rural areas offer more economic mobility for people who grow up lower in the income distribution – that is, a better chance of rising in society.

I put together a map of Minnesota and one of the Upper Midwest that shows this, and you can check it out here.