Income inequality has become a hotly debated topic globally. According to the CIA World Factbook, U.S. income inequality ranked 41st highest among 156 countries in 2017 (i.e., 74% of countries have a more equal income distribution). According to the Congressional Budget Office, the top 1% of income households earned about a 9% share of the pre-tax income in 1979, versus 19% in 2007 and 17% in 2014. For after-tax income, these figures were 7%, 17%, and 13%, respectively. These figures indicate the share of income earned by top earners more than doubled between 1979 and 2007, then fell somewhat following the Great Recession, and the higher tax rates and re-distributive policies applied by President Barack Obama in 2013 (i.e., expiration of the Bush Tax Cuts for the top 1% and subsidies for lower income persons via the Affordable Care Act). Recasting the 2012 income using the 1979 income distribution (representing the more egalitarian 1950-1980 period), the bottom 99% of families would have averaged about $7,100 more income. Income inequality in the United States has grown from 2005 to 2012 in more than 2 out of 3 metropolitan areas.

How many percentage points in pre-tax income did the top 1% gain from 1979 to 2014?
8