Angela Chen, writing for the Wall Street Journal:

As of 2010, about 2.1 million U.S. women were using an IUD, the highest level since the early 1980s, according to the Guttmacher Institute, a reproductive-rights organization with offices in New York and Washington, D.C. Of women using contraception, about 5% use an IUD, which is still significantly less than the 27% who use the hormonal pill—the most popular method.

The IUD is 20 times more effective than birth control pills, the patch or vaginal ring, according to a 2012 study published in the New England Journal of Medicine. That is because the IUD virtually eliminates the risk of human error.