Some 79% more men than women attended America’s colleges and universities when one of us (Mr. Vedder) was an undergraduate in 1959. Women now greatly outnumber men on campuses. The Journal reported recently that men now make up only about 40% of college students. From spring 2019 to spring 2021, the number of collegiate male students fell by more than 535,000, well over triple the modest 154,000 decline observed for women, according to National Student Clearinghouse data.

Between 1959 and 2021, the number of male students for every 100 women fell by an extraordinary 62%. The decline in the 1960s and 1970s can be explained as women simply catching up with men. But the decline in men on campus continued in the late 20th century, long after parity had been reached and gender equality had improved.

Why has this been happening? Here are four reasons. First, the initial surge in female enrollment is explainable by a rapid rise in female labor-force participation. Women realized that a successful career would be enhanced by a college education. Meanwhile, women are marrying later—at age 28 on average in 2020, up from 20.3 in 1960.