A report from the Congressional Research Service (CRS) analyzes (1) how the income distribution of the undergraduate population has changed over time; (2) the relationship between student income and certain student demographics, such as race and dependency status; and (3) how the income distribution of the undergraduate population compares with that of the population of individuals who do not have a post-secondary degree.
The report can be obtained at https://fas.org/sgp/crs/misc/R45686.pdf.