Commencement speaker and billionaire Robert F. Smith announced Sunday he will donate an estimated $40 million to pay off the student debt for the 400 students graduating at the historically black, all-male Morehouse College, the Atlanta Journal-Constitution reports.

Why it matters: Student debt in the United States has reached $1.5 trillion. Studies show student debt causes lower incomes and is the No. 1 stressor of millennials.

Smith, a philanthropist, tech investor and founder of Vista Equity Partners, already donated $1.5 million to the college.