ARC researcher Mike Carnathan said the projections are based on national forecasts that use "a respected and oft-used econometric model" -- one based on things like jobs, birth rates, migration and other demographic factors. The ARC's interactive dashboard -- the full version of which can be found here -- has population projections for 20 counties in the greater metro Atlanta region.
*Forsyth County is actually expected to grow the most, percentage-wise, by 2040, more than doubling its population to just over 430,000.
*Other counties with the most expected growth: Barrow (81 percent), Paulding (74), Coweta (70) and Cherokee (68).
*Cobb, DeKalb and Clayton are expected to have the 20-county region's least growth, percentage-wise, at 22, 22 and 23 percent, respectively. Cobb will have a population of about 885,000 residents in 2040, the ARC projects, and DeKalb will land around 874,000. Clayton is expected to have a population around 327,000.