Harvard University disclosed Friday that former investment chief Stephen Blyth received $14.9 million in 2015, making him one of at least three highly compensated employees at the endowment who have left the underperforming fund. Blyth, 49, ran Harvard Management Co., the university’s nonprofit investment arm, for about 18 months, before leaving last May for personal reasons. His pay, which includes salary and bonus, was larger than the $11.6 million median compensation in 2015 for a chief executive officer in an S&P 500 company, according to data compiled by Bloomberg.