On International Women’s Day, other nations have more to celebrate when it comes to women in government. In the past two decades, the US has sunk from 52nd in the world for women’s representation to 104th today, according to data compiled by the Inter-Parliamentary Union. In the past year alone, the US has dropped nine places — from 95th to 104th — among more than 190 countries.

US rank in women’s government dropped 9 spots in the past year

And that’s a problem. Women and girls currently make up more than half the population in the US, but they’re represented by a Congress made up of 80 percent men. This isn’t just an issue in terms of equal representation — the proportion of women in government profoundly affects how all of society views women.

Other countries do it better

How did 103 nations outpace the US in women’s representation over the past 20 years? A mix of constitutional amendments or legislation for some countries and voluntary party quotas for others. Today, around half of the nations in the world use some kind of gender quota in government, according to the Global Database of Quotas for Women.

Take, for example, Bolivia. Twenty years ago, it ranked 98th for women’s representation, and as recently as 2008, only 16.9 percent of its representatives were women. But in 2009, the country passed a constitutional amendment requiring equal gender representation in government. The Bolivian legislature is now 53.1 percent women and ranks second in the world.

Percentage of women in lower or single house

But legislation isn’t necessary to put more women into office. Consider Sweden: In 1971, 14 percent of the country’s legislators were women. The next year, Sweden’s Liberal Party set a quota: 40 percent of its candidates would be women going forward. Other parties followed in the 1970s and ’80s, setting their own quotas for women candidates. Now Sweden’s government is 43.6 percent women, ranking sixth in the world.

The system didn’t require any change on the part of the government; no constitutional amendments were required. Rather, all that had to happen was for the parties to decide that gender representation was a priority.

Why American women are being left out of the political system

It’s not that the US hasn’t made any progress in equal representation. In fact, the percentage of women in Congress has risen steadily at about 1 to 2 percent every election. But the number of congresswomen in the past election didn’t budge at all, remaining at 104. (In one small sign of progress, women of color quadrupled in the Senate, from one senator to four.)

Number of women in Congress by congressional session since 1917

Beyond the lack of any kind of gender quota, incumbency is the biggest reason American women are being left out of the political system. On average, about 89 percent of House members run for reelection — and around 97 percent are reelected. This means that every election cycle, about 86 percent of the seats are already taken.

Legislators have started to serve longer too. In the 20th century, the average Congress member served about four years. Now the average House member spends 10.3 years in office and the average senator serves 9.7 years. This, again, creates less opportunity for new politicians to serve.

But it turns out that women are also less likely to run for office in the first place. A study by Jennifer Lawless and Richard Fox has shown that women consistently underestimated their qualifications and perceived themselves differently than men who had nearly identical credentials. Women were also more likely to perceive campaigning as harder and were less likely to have anyone — whether a friend or a party official — encourage them to pursue political office.

Perhaps the biggest takeaway from Lawless and Fox’s study is this: Potential women candidates were 15 times more likely than men to be responsible for the majority of child care, and six times more likely to manage most housework. With those kinds of obligations, who has the time to run for office?

More women in government affects how society thinks of all women

One reason we might care about increasing women’s representation in government is if we think they will govern differently — if we think different laws will get passed or certain topics will get discussed at greater length.

There is research that shows this to be true. Georgetown professor Michele Swers’s study of women’s policy impact in government shows that women consistently co-sponsor more bills related to women’s health than their male counterparts, regardless of liberal or conservative ideology.

But more importantly, having more women in government changes how society thinks about all women — and how young women think about themselves.

Christina Wolbrecht, a political scientist at Notre Dame University, has found that adolescent girls are more likely to indicate an interest in running for office during years when there is lots of media coverage of women in politics.

Another one of her studies looked at 23 developed countries with varied levels of women in government. It found that in the countries with more female legislators, young women were more likely to participate in politics and have political discussions, and that young women expressed a greater interest in becoming politically active in the future.

Or consider an influential 2012 study in the journal Science, which looked at what happened when India randomly assigned some political positions to women. In villages assigned to have female “pradhans” — essentially city council chiefs — parents became more aspirational in what they expected of their daughters.

The fraction of parents who believed that a daughter’s occupation (but not a son’s) should be determined by her in-laws declined from 76 percent to 65 percent. Adolescent girls in those areas also became less likely to want to be housewives — and the gap in educational attainment between young boys and young girls completely closed.

All of this research shows that it can matter hugely when we see someone like ourselves in a position of power. It shows: You can do this too. But right now, too many women and girls in the US aren’t getting this message.

Read more about the lack of women in Congress here.