While women still earn 77 cents for every dollar that men make in the United States, the gender wage gap has closed significantly over the past several decades. Now, for the first time ever, a new study has connected the narrowing of that pay gap to increased access to birth control pills.
The University of Michigan study, which analyzed the careers of 4,300 women, shows that the earlier a woman can start taking birth control pills, the more likely she is to earn higher wages later in life.
About one-third of women's wage gains throughout the 1990s can be attributed to changing laws in the 1960s and 70s that lowered the age at which women could legally access the pill.
"We found that women who had early access to the pill in the 1960s and 1970s earned 8 percent more on average by the 1980s and 1990s than women without early access," said Martha Bailey, a research affiliate at the U-M Institute for Social Research who authored the study.
When some states dropped the legal access age from 21 to 18, the report found, contraceptive use among 18- to 20-year-olds doubled. This development, in particular, allowed more college-aged women to finish school without being interrupted by an unplanned pregnancy.
"As the pill provided younger women the expectation of greater control over childbearing, women invested more in their human capital and careers," said Bailey. "Most affected were women with some college, who benefited from these investments through remarkable wage gains over their lifetimes."
This study is particularly relevant considering the recent birth control debates in Congress and the Obama administration. President Barack Obama faced a significant backlash from women's rights groups after his administration rejected a proposal to increase young women's access to Plan B, the morning-after pill. And more recently, Congress has debated whether employers should be required to cover contraception with no co-pay for the women they employ.
While most of the debate over birth control has revolved around health consequences and religious liberty issues, the U-M study shows that allowing women to decide when and if to have children also has a significant economic impact on them.
"The pill's availability likely altered norms and expectations about marriage and childbearing," said Bailey. "It also likely affected the decisions of companies to hire and promote women."
More:Contraception Wage Gap Obama Birth Control Contraception Debate Birth Control Obama Contraception
HuffPost Women sends stories about relationships, politics, sex, work, culture and body image, straight to your inbox three days a week. Learn more