The data this week comes from many different sources but originally came from the US Department of Education.
The details of the datasets can be found here.
Before 2000, the only records available are for 1985 & 1995. There are
also gaps in the data for private institutions from 2006-2008/2010-2012
& 2006-2011 for public institutions.
The data seems to be inconsistent for 2017-2018, so it may be
unreliable. The total cost was the same across all income levels for
2017, unlike the other years. An error in the documentation may be the
cause of the dip in those two years.
In this case, diversity/minorities = all students who are not
categorized as white, race unknown, or a nonresident.