Millennials today (18 – 34) are 56% white, compared to pre-millennials (35 and older) who are 68% white. The rise of the non-white population of voting age is mainly due to Hispanics, although Blacks and Asians are also growing in numbers. The large waves of immigration to the U.S. in the 1980s and 1990s, especially from Latin America and Asia, coupled with the aging of the white population, made millennials a more racially and ethnically diverse generation than any that preceded it. (Brookings Institution, here)
This explains the current surge in the percentage of voting age persons who are non-white. Between 2000 and 2020 non-white voting age persons rise from 24% to 33% of the total:
Adding more insight, for the first time since the Census Bureau has released annual statistics, they show for 2016 and 2017 an absolute decline in the nation’s white non-Hispanic population—accelerating a phenomenon that was not projected to occur until 2023.
And, in 2014, one in five births (791,000) in the United States was to an immigrant mother, contrasted with 13% of the total population being foreign-born. Immigrant mothers accounted for half or nearly half of births in Miami, San Francisco, and San Jose, CA.