CASPER, Wyo. (AP) — Wyoming will study why women in the state earn less than two-thirds as much as men.

Wyoming ranks behind all U.S. states and Washington, D.C., for its wide gap between the incomes of women and men. The National Partnership for Women and Children finds that women in Wyoming who work full-time and year-round earn 64 percent as much as men.

Last winter, Wyoming lawmakers approved a bill directing the state Department of Workforce Services to study the issue. A report is due by October, 2018.

One theory for Wyoming's wide wage gap is more men than women work in the state's high-paying jobs in the energy industry.

New York, Delaware and Florida have the nation's smallest gaps between men's and women's wages.