Reasons for the gap between men and women in higher education date back to the early 1900s, according to a new study from the National Bureau of Economic Research.

The report, conducted by three Harvard University economists, emphasizes that the numbers of males and females in college were roughly equal between 1900 and 1930. At that time, women began seeking careers that required college education, beginning the trend that exists today, the study says.

Among the factors cited in the study that dictated female college figures in the ’30s was the increase in bans on married women working during that time, according to the study.

Because of this, the authors said, the modern patterns in the college population were always present, but only kept dormant in the mid-1900s by social factors.

It was in the 1980s when women began gaining on the male population, according to the study, because of several factors, including the women’s movement and an influx of careers open to women.

The authors also suggested other factors for hikes in female enrollment. One is that changes in societal values have meant that more women hold jobs for significant portions of their adult lives, or their entire adult lives.

Also, since the wage difference between college-educated women and those without college degrees has always been greater than that of men, the authors wrote, women have more monetary incentive to attend college. Women are also focusing on the importance of jobs by focusing more on college.

The other major factor they cite is that women do better in high school. They are not only more likely to study, the authors said, but also to take the courses needed for college and to do well in those courses than are men.

Male high school students are also more likely to have behavioral problems, the study stated.