During the last three decades, the real income of african american families in the united states has

Changed very little.

If anything, the income of black Americans may have dropped somewhat. In 2016, the median income for an African American household was $39,490, according to U.S. Census Bureau figures.  Adjusted to 2016 dollar values, the median income for an African American household in the year 2000 was $41,363. 

The income of African American households has consistently lagged behind that of other groups.   Overall median average household income for American households in 2016 was $59,039.  For white Americans it was
over $65,000, and for Asian Americans, over $81,000.