Interesting... in 2018, 2017, and 2016 it only really increased by 1 or 2 percentage points.
https://www.census.gov/library/publications/2019/demo/p60-26...
https://www.census.gov/library/publications/2018/demo/p60-26...
https://www.census.gov/library/publications/2017/demo/p60-25...