If states were individual countries, Colorado, the state with the most women in the legislature, would have the 10th most female legislators in the world. The federal government, meanwhile, wouldn't even make it into the top 100.

America's gender gap is explained by a lack of women running for office

About 20.4 percent of legislative seats around the world are held by women, according to the Quota Project. The federal government falls short of that: 18.3 percent of US House members and 20 percent of US senators are women. But the story is a little better in the states: 24.2 percent of state legislators are women, with Colorado leading the states at 41 percent.

Women make up nearly 51 percent of the US population, so they would need to make up more than half of Congress and all state legislatures to achieve equal representation.

America's gender gap is in part explained by a lack of women running for office. As Vox's Ezra Klein wrote for The American Prospect, women tend to do about as well as men when they actually run. The problem falls on a lack of representation: women are considerably less likely to run for office than men. If women were better encouraged by society as a whole to run for office, the gender gap could be closed.

The gender gap is a problem in all national governments. Only Rwanda, which requires that at least 30 percent of its legislature is made of of women, has a legislature with a female majority.

There are some other countries that do surprisingly better than the US in this regard. About 27.7 percent of the legislature in Afghanistan, which ranks 175 out of 186 in the UN's Gender Inequality Index, is made up of women. Most of that is explained by a constitutionally established quota in Afghanistan: women must make up more than 27 percent of the Afghan legislature.

Compare the US and other countries in this massive chart, made by David Mendoza: