WINCHESTER — The area’s population growth is projected to continue outpacing the state’s through 2040, according to new population projections released by the University of Virginia’s Weldon Cooper Center.

In Winchester and Frederick and Clarke counties, the combined population will increase 24.5% by 2040, from 133,428 to 166,064, projections show.

Projections by locality indicate:

Winchester’s population of 28,804 will grow to 31,005 by 2030 and 32,770 by 2040.

Frederick County’s population of 90,115 will increase to 104,608 by 2030 and 117,452 by 2040.

Clarke County’s population of 14,509 will grow to 15,279 by 2030 and 15,842 by 2040.

Since 2010, the Winchester area has been one of the fastest-growing regions in Virginia. Overall, however, Virginia is experiencing its slowest population growth in almost century, according to data from the Weldon Cooper Center, which does official population projections for the commonwealth.

Even still, the area’s faster-than-average growth rate represents a slowdown from previous decades, Hamilton Lombard, a Weldon Cooper researcher, said on Monday.

Since World War II, Frederick County has regularly “outpaced Texas” in its rate of growth, he said. In the 1980s, 1990s and 2000s, the county had a more than 30% growth rate. But population growth from 2010 to 2020 may drop to 16%, estimates show. And rates for future decades are projected to go as low as 12%.

The state’s average growth rate for this decade is projected to be 8%.

“People aren’t having enough kids to replace themselves,” Lombard said, explaining the parts of Virginia that are growing are doing so because of people moving there.

Growth in Winchester and Frederick and Clarke counties is mostly made up of retirees and “established families” relocating here from the Washington, D.C., area, Lombard said. Births represent a minor part of the area’s population growth.

It’s unknown what will happen after 2030, when the Baby Boomer generation will mostly be 85 years old and older and their numbers start to decline. If younger generations don’t start having more children, the population dip could start to spike, Lombard said.

That decline is already happening in many rural counties throughout Virginia, particularly in the southern and southwestern areas. In those regions, there are not enough new residents or births or immigrants to replace the people who are dying. More than half of Virginia’s counties have experienced population decreases since 2010, according to Weldon Cooper data. And all Virginia counties bordering Tennessee and Kentucky have experienced population declines this decade.