For the many Georgians who can’t find an inch of tire space on I-285 at rush hour or an open patch of sand on the beach at Tybee, one question likely keeps running through their minds:

Where did all these people come from?

The answer: Not all where you might think.

Georgia’s population grew by nearly 116,000 people in 2017 — the sixth biggest jump among all states, according to the U.S. Census Bureau. But that’s not because more babies were born here. For the third consecutive year, the total number of births in Georgia went down, according to a provisional report from the National Center for Health Statistics.

The drop is in keeping with the trend of declining birth totals nationwide. One major explanation, experts say, is younger women who are delaying or forgoing marriage and childbirth for educational and employment opportunities that may have been unavailable to earlier generations.

On Thursday, the U.S. social security administration announced their annual list of popular baby names, broken down by state. Naming popularity is based on their database of applications for new Social Security cards. In 16 states, Liam was the most popular name for baby boys in 2017. Emma, came in on top for girls nationally Popular names in the Northeast region include Logan, Benjamin, Lucas, Noah. William in the South and Oliver and James in the Northwest. For girls, Ava is popular in the south. Charlotte and Olivia also dominated in both the East and West.

But in Georgia’s case in particular, it also underscores how other factors besides birth and death drive population change.

“Population grows or declines in two basic ways, through in-migration or natural change,” said Mike Carnathan, group manager for research and analytics at the Atlanta Regional Commission. “When the economy is going good, our population grows more through in-migration. When the economy is bad, it’s more through natural increase.”

“In-migration” refers to the number of people moving into an area. When more move in than move out, that’s considered positive net migration. Across Georgia in 2017, net migration accounted for a larger share — 58 percent — of the population growth than did natural increase (the total number of births minus deaths statewide).

There were 129,210 live births in Georgia in 2017, according to the provisional birth data report from the NCHS. (The final version of the annual report, including more detailed state-by-state statistics, will be released near the end of this year or in early 2019.) That’s down from 130,042 births in 2016 and 131,404 in 2015, and puts Georgia on the same footing as the rest of the country when it comes to declining birth numbers.

In 2017, the number of births in the United States was the lowest in 30 years, according to the NCHS. It was the third consecutive year that births declined nationwide. Teenagers and women in their 20s showed the biggest declines:

Nationally, the 2017 provisional birth rate (the number of births per 1,000 women in a specific age group) for teens ages 15-17 was 7.8, down from 8.8 in 2016. For teens ages 18-19, the provisional 2017 rate was 35.1, down from 37.5 in 2017. In Georgia, the birth rate for teens ages 15-17 was 10.2 in 2016 (the most recent year available), down from 11.4 in 2015, according to the NCHS reports. For Georgia teens ages 18-19, the birth rate was 44.4 in 2016, compared to 47.4 in 2015.

Birth rates also declined notably among women in their 20s, both nationally and in Georgia (see box).

“This definitely is what I’m seeing clinically,” said Dr. Melissa Kottke, an associate professor in the department of gynecology and obstetrics at Emory University School of Medicine and medical director of the Grady Teen Clinic. Kottke described the ongoing decline in teen births in particular as “a success story.”

Just as many women are choosing to marry later — the average age of first marriage was 27.4 years in 2017, up from 24 in 1990 — they’re also waiting to have children to pursue their education or become more firmly established in jobs and careers.

“It’s a fundamental shift in lifestyle having to do with women’s role in the economy,” said Carnathan of the Atlanta Regional Commission. “They are now full participants.”

But, declining birth rates or not, things aren’t about to get any less crowded around here. Georgia’s population is projected to keep right on growing at the expense of some other states. (At 10,429,379, according to the most recent Census Bureau estimates, Georgia is now the eighth most populous state.) A lot of that growth will come in the 20-county metro Atlanta area, which the ARC forecasts will have an additional 2.5 million residents by the year 2040. (The same area had 5,884,736 people as of July 2017 population estimates from the U.S. Census Bureau.)

Just don’t expect the majority of them to be born here.

“A lot of (the population growth) will come from natural increase, but more than that is going to come from people moving here for jobs,” said Carnathan. “You’d rather see your population increase more by in-migration. That means the economy is healthy, you’re having a good job churn and people are able to move here and move around.”

Except maybe on I-285 at rush hour.

BY THE NUMBERS

Birth rates among women in their 20s in the U.S. and Georgia, as reported by the National Center for Health Statistics.

Nationally, the 2017 provisional birth rate was 71.0 per 1,000 women ages 20-24, a decrease from 2016’s rate of 73.8. For those ages 25-29, the 2017 provisional rate was 97.9, down from 102.1 in 2016.

In Georgia, the 2016 birth rate (latest year available) was 85.1 per 1,000 women ages 20-24, a decrease from 2015’s rate of 88.8. For those ages 25-29, the 2016 birth rate was 103.9, down from 106.5 in 2015.