Well-paying jobs that don’t require a college degree are multiplying at the fastest rate in three decades, offering more Americans a path to the middle class. But economists warn that one group is missing out: women.

A new report from Georgetown University found there are now about 13 million jobs nationwide that require only a high school diploma and pay at least $35,000 annually, a higher wage than most entry-level service roles.

Three-quarters of them, however, belong to men.

“If you don’t have that degree, you better be a guy,” said Nicole Smith, chief economist at the Georgetown University Center on Education and the Workforce.

Men have long dominated manufacturing, mining and construction — some of the best-paying fields open to high school graduates.

These goods-producing positions swelled 3.3 percent in the year before July, the strongest pace since 1984, according to a recent Washington Post analysis.

The upswing after a long lag has exacerbated the country’s labor shortage — there are more jobs open in the United States than workers to fill them. So employers and unions lately have tried to recruit more women into traditionally masculine trades. The effort has introduced paid maternity leave, for example, to some ironworking roles.

But the share of female employees in such areas has remained stubbornly tiny, Smith said. Women hold fewer than a third of the country’s factory jobs, which can command salaries above $50,000, and they fill just 9 percent of construction positions. (The average annual income, per the Bureau of Labor Statistics: $40,000.)

Analysts say blue-collar jobs, even with increasing perks, have an image problem — society still doesn’t expect to see a woman wielding a jackhammer — and women who try to break into the industries face discrimination from bosses and colleagues.

Nearly 9 in 10 female construction workers have dealt with sexual harassment on the job, one Labor Department study found.

It’s hard to say how long the blue-collar growth spurt will last. A million more goods-producing jobs existed before the recession, The Post’s Heather Long reported. Today’s gains could vanish if the economy slips.

Since the downturn, women without degrees have cycled into more enduring — if worse-paying — types of work.

They tend to make a living in hospitality (51 percent female), child care (94 percent female), health care (78.5 percent female) and bookkeeping (60 percent female), government figures show.

Secretarial and administrative roles typically provided bigger paychecks to women with high school diplomas — median pay: $37,870 per year — but such work is shrinking.

The Bureau of Labor Statistics projects a 5 percent job loss in the field over the next decade as more companies automate tasks like scheduling, record-keeping and data collection.

Nowadays, the jobless rate for women with only a high school diploma (4.7 percent) is higher than for men with the same educational attainment (3.5 percent). They’re also making less money.

Among workers without college degrees, women earn an average of 78.6 percent of what men take home, according to a recent analysis from the Institute for Women’s Policy Research. (That ratio is 80.4 percent in the broader economy.)