According to a new report in Forbes, the city of Atlanta has had the largest increase in its senior population since 2000. Overall, the senior population in America has grown 29 percent, while overall population growth is just 12 percent. In contrast, Atlanta’s senior population grew by a whopping 73.5 percent from 2000 to 2013!

According to the article Aging America: The U.S. Cities Going Gray the Fastest, the primary causes for this increase in the senior population are that the baby boomer generation has reached 65 years of age and the U.S. fertility rate has dropped.

To find the cities that have the fastest-growing senior population, the researchers looked at the change from 2000 to 2013 in the share of the seniors in the populations of the nation’s largest metropolitan areas. What the researchers found was that the metropolitan areas that have seen the biggest jump in senior population are the same cities that attract millennials, families and working adults. Typically, the senior population hasn’t moved to the city in large numbers; instead, they moved there at a younger age for job opportunities or better lives and now they’re aging there.

In 2000, just 7.7 percent of Atlanta’s population consisted of seniors compared with 10.13 percent in 2013, or 572,534 residents. Raleigh is No. 2 on the list with 10.2 percent of its population over the age of 65, while Austin is No. 3 on the list with seniors comprising 9.2 percent of its total population.

According to the article in Forbes, cities are expected to age even faster over the next 15 years in the U.S., meaning active adult and senior living communities will continue to grow in metro Atlanta and other American cities.