It’s tempting to think of the United States as a powerful behemoth that towers over its neighbor to the north, especially when it comes to economic metrics. The U.S. labor force and GDP dwarf Canada’s; California and Texas alone had larger individual GDPs than Canada’s $1.5 trillion in 2016. But Canada has the U.S. beat when it comes to a measurement that more economists are recognizing is critical to economic growth: the participation of women in the labor force.

Both countries have seen more women moving into the workforce over the last 40 years, with 74% of Canadian women and 66.2% of American women holding jobs today. However, in Canada, the participation gap between working men and women in the workforce has been shrinking, while in the U.S., that gap has remained stubbornly wide for more than a decade. It sits at about 11% today, only slightly less than it was in the mid-1990s.

A new report by Citi Global Perspectives and Solutions (GPS) examines women’s contributions to the global economy and the potential benefits of women’s economic empowerment. Chief among those benefits: explosive growth.

But at a time when growth is a huge part of the national political conversation, creating favorable conditions for women in the workforce is still not a policy priority in Washington. The U.S. remains something of an outlier among developed nations, and ranks lower than most of its cohort when it comes to gender equality in the workforce, sitting 45th on the United Nation’s Gender Equality Index, well below Canada at 18th.

Why does the U.S. sit so low on the list? According to Tina Fordham, Citi’s chief global political analyst and a co-author of the report, “These are relative rankings. Other countries, including Canada, started making a real effort to level the playing field decades ago. The United States did not institute any of these kinds of policies. So we fell.”

Dana Peterson, North America economist with Citi Research and another co-author of the report, explains: “In Canada, they’ve actively tried to improve access to full-time paid work for women and have made a number of government interventions, such as guaranteed paid-family leave, tax benefits for families with children, and pay equality legislation. And, at the corporate level, there’s been a concerted effort to make sure that women are being compensated adequately for the same types of work.”

American women, especially those tasked with caring for children or elderly relatives, confront sizable barriers to full participation in the workforce. Beyond the tax penalties second earners often face (also known as the “marriage penalty”), the high cost of childcare and unstable working conditions keep many women sidelined.