The teen birth rate in America’s small towns is 63 percent higher than in its biggest cities, a new government report reveals.

In 2015, there were 18.9 births for every 1,000 women between the ages of 15 and 19 living in counties with large urban areas, according to a report published Wednesday by the Centers for Disease Control and Prevention. That compares with 30.9 births per 1,000 women in the same age group who lived in rural counties, the report said.

In between were counties with small- and medium-sized cities and suburbs. There, the birth rate was 24.3 babies per 1,000 women ages 15 to 19.

Though the teen birth rate varied widely between cities, towns and hamlets, municipalities of all sizes had one thing in common: All experienced steady declines in teen birth rates between 2007 and 2015, federal data show.

Large urban counties recorded the biggest drop over those eight years. In 2007, the birth rate for 15-to-19-year-olds was 38.1 births per 1,000 women. It has since plunged by 50 percent.

Next came counties with smaller urban areas, where the teen birth rate is now 44 percent lower than the 43.1-per-1,000 rate seen in 2007.

Rural counties started out with the highest birth rate — 49.1 births per 1,000 women ages 15 to 19 — and saw it fall 37 percent over eight years.

Here’s another way to appreciate the change: Urban counties in every single state (plus the District of Columbia) recorded a decline in the teen birth rate between 2007 and 2015. In 17 states, the teen birth rate in urban areas was cut at least in half. These states included Arizona, California, Colorado, Connecticut, Florida, Georgia, Maryland, Massachusetts, Minnesota, Mississippi, New Jersey, New Mexico, North Carolina, Rhode Island, Utah, Vermont and Virginia.

Likewise, the teen birth rate for rural counties fell in all 46 states that reported reliable data. Two states — Colorado and Connecticut — recorded a decline of at least 50 percent between 2007 and 2015. (New Jersey, Rhode Island and the District of Columbia do not include any rural counties.)

Across racial and ethnic groups, the researchers consistently found that the more urban a county, the lower the teen birth rate.

For non-Latina white women, the 2015 teen birth rate in rural counties (26.8 per 1,000) was 2.5 times higher than the rate in large urban counties (10.5 per 1,000). For non-Latina black women, the teen birth rate in rural counties (39.6 per 1,000) was 36 percent higher than in large urban counties (29.1 per 1,000). And for Latina teens, the birth rate in rural counties (47 per 1,000) was 50 percent greater than in large urban counties (31.4 per 1,000), according to the report.

The authors of the report don’t know why the teen birth rate was lower — and falling faster — in large urban areas than in rural ones. They did not study abortion rates between 2007 and 2015, nor did they examine whether schools in some counties were more or less likely to promote the use of birth control, or abstinence.

The study was based on data collected by the National Vital Statistics System and from the National Center for Health Statistics’ Urban-Rural Classification Scheme.