Many factors have retarded growth since the 1970s. One of the most important is rising inequality. During 1917 to 1948, the gap between the wealthiest and poorest Americans decreased. Since 1970, that pattern reversed, as the top 10 percent of income earners pulled away from the bottom 90 percent. In 2013, income for the bottom 90 percent was lower than it had been in 1973, even as the income of the top 10 percent almost doubled.