Walk into a classroom of environmental engineering students and, odds are, nearly half of them will be women. Now head next door to an electrical engineering class: you’ll likely find eight men for every woman.

The failure to recruit and retain more women in electrical and computer engineering—large fields with lots of students—is a major reason the representation of women in U.S. engineering as a whole has remained so low for so long. Last year, only 18.1 percent of all bachelor’s degrees in engineering awarded by U.S. schools went to women. And things are getting worse: that’s the lowest level in more than a decade.

Electrical engineering has one of the lowest proportions of bachelor’s degrees awarded to women, a meager 12.4 percent last year, down from an already low 14 percent the year before, according to the American Society for Engineering Education. It’s not the lowest—computer engineering, at 9.2 percent, is at the bottom—but its proportion of women is less than a third that of biomedical or environmental engineering.

Experts see in these differences a larger pattern: ”Women seek areas where the societal benefits are very apparent,” says Diane Matt, executive director of the Women in Engineering Proactive Network, in Denver. ”They want careers that have a positive impact on the world.”

Not that there aren’t social benefits to all areas of engineering—the problem is one of perception. Eleanor Baum, dean of engineering at Cooper Union, in New York City, and an IEEE Fellow, says electrical engineers are not sending a compelling message about their profession. ”Instead of trying to explain what’s a power engineer, what’s a computer engineer, and so on, we should focus on a single coordinated message: electrical engineers do this, and this affects people’s lives.”