When, during her acceptance speech for the Oscar for Best Supporting Actress, Patricia Arquette said, “It’s our [women’s] time to have wage equality, once and for all and equal rights for women in the United States of America,” the crowd went wild. Then the controversy kicked in, as people dissected her language for nuance, the way they might parse the State of the Union.

But, here are some facts: The median earnings of women still trail those of men, according to the most recent data from the Bureau of Labor Statistics. Overall, women earn 82.1% of what men do, and the pay gap widens as women get older and enter the child-bearing years. While young women aged 16 to 24 earn 92% of men that age, women aged 25 to 54 earn just 81% of their male counterparts.

Women’s wages, however, have shown some improvement. At every level of education, the boost to women’s weekly earnings has significantly outpaced those of men.

Gender gap graph

And overall, the gender pay gap has been narrowing. In 1979, women made less than 65 percent of what men did, but as you can see from this graph, women are catching up, albeit slowly.

Gender gap graph

Still, there remains a significant gender pay gap, and some fields have bigger gaps than others. Fortune examined data from the BLS Current Population Survey and compared median weekly earnings of full-time wage and salary workers by occupation and gender, excluding occupations that lacked gender-specific data, and sorted to find the specific job types in which the gender pay gap was largest.

These are the 20 with the biggest gaps. Interestingly, half of them are white-collar jobs, including the one with the biggest pay gap.

What’s the cause? Countless studies have been devoted to parsing the data. A variety of explanations have been posited, ranging from the choices that women make — to work fewer hours, choose lower-paying professions — to women’s negotiating skills to employers’ tendency to “disproportionately reward” long hours in offices, which tends to penalize women with care-giving responsibilities.

While the debate is likely to rage on, it’s clear that gender-based pay gaps exist in most occupations. Here are the 20 jobs that have the biggest gender wage gaps.