Within two years, if current trends hold up, Houston County's population will pass Bibb County's.
Estimates released by the U.S. Census Bureau this week show Houston gaining almost 200 people a month since the 2010 census. Bibb continues to lose about 30 residents a month.
On July 1, 2013, the Census said, 154,721 people lived in Bibb County, 147,658 in Houston.
But if Houston's growth and Bibb's decline continues, their roles would reverse by February 2016.
The 1990 Census showed 89,208 people living in Houston, 149,967 in Bibb. Ten years later, Bibb's population was about 43,000 people bigger.
Houston's growth since then has been helped by Robins Air Force Base, the state's largest employer.
Meanwhile, this week's Census release shows that most of Central Georgia is shrinking.