5Over the years, certain demographic groups have fared better than others in moving up the economic ladder. Since 1971, older Americans (ages 65 and older) and African Americans have made notable progress in moving up the income tiers. But overall, both groups are still overrepresented in the lower-income tier. Married adults also made significant progress over this 44-year period, and women overall made greater economic gains than men.
Americans without a college degree stand out as experiencing a substantial loss in economic status since 1971, as do young adults ages 18 to 29. Hispanics overall are also more likely to be in lower-income households than in 1971, a change driven by the increasing share of immigrants in the Hispanic population in the past four decades.
http://www.pewresearch.org/fact-tank/2015/12/10/5-takeaways-about-the-american-middle-class/