The gender pay gap has narrowed substantially since the Equal Pay Act was signed in 1963. Still, the typical woman working full time in the United States earns $40,022 a year — or only about 80% of the median annual income for men working full time of $50,119.

A study conducted by the Pew Research Center estimates a woman would need to work an additional 44 days a year to earn the same amount as her male counterpart.

Several explanations — some real, some imagined — are often given to account for the discrepancy. For example, women typically are out of work longer during pregnancy, women leave the workforce sooner, and women are more likely to pursue lower-paying careers. However, even when accounting for all these factors, there still appears to be a gap.

In the Washington D.C. metro area, the wage gap is not as pronounced. The typical woman working full-time in Washington D.C. earns $57,894 a year, or about 82.4% of the $70,280 median income of men in the metro area.

The gender pay gap in Washington D.C. also varies by industry. The largest earnings gap between men and women in the metro area can be found in production occupations, where women earn only 63 cents for every dollar earned by men.

The pay gap also tends to be worse in professions in which women have historically been excluded. The typical female in the sales profession in Washington D.C., for example, earns only 64 cents for every dollar a man in the field earns.