| | Decatur, GA | Tuscaloosa, AL | United States |
| Population | 24,334 | 99,252 | 329,725,481 |
| Female Population | 52.6% | 52.0% | 50.5% |
| Male Population | 47.4% | 48.0% | 49.5% |
| Median Age | 38.6 | 29.5 | 38.4 |
| space3 | | | |
| Population - 2010 | 19,700 | 90,409 | 309,327,143 |
| Population - 2000 | 18,147 | 77,906 | 285,036,114 |
| Population - 1990 | 17,336 | 77,759 | 251,960,433 |
| Pop. 2000 to Now | 41.4% | 32.0% | 15.6% |
| Pop. 1990 to Now | 48.0% | 32.2% | 30.8% |
| space4 | | | |
| Population Density | 5,485.6 | 1,608.4 | 93.4 |
| Land Area | 4.4 | 61.7 | 3,531,905.4 |
| Water Area | 0.0 | 10.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Decatur, GA | Tuscaloosa, AL | United States |
| Age 0 to 4 | 6.9% | 5.5% | 5.9% |
| Age 5 to 9 | 10.7% | 5.2% | 6.1% |
| Age 10 to 14 | 10.2% | 4.7% | 6.6% |
| Age 15 to 17 | 4.4% | 2.8% | 3.9% |
| Age 18 to 20 | 3.3% | 13.6% | 4.0% |
| Age 21 to 24 | 2.4% | 10.9% | 5.2% |
| Age 25 to 34 | 7.6% | 14.7% | 13.8% |
| Age 35 to 44 | 15.3% | 10.8% | 12.9% |
| Age 45 to 54 | 16.0% | 8.9% | 12.6% |
| Age 55 to 59 | 6.5% | 4.7% | 6.7% |
| Age 60 to 64 | 5.3% | 5.1% | 6.3% |
| Age 65 to 74 | 6.9% | 8.0% | 9.6% |
| Age 75 to 84 | 3.0% | 3.8% | 4.5% |
| Age 85 and over | 1.6% | 1.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Decatur, GA | Tuscaloosa, AL | United States |
| White | 66.9% | 47.4% | 59.4% |
| Black | 15.6% | 44.0% | 12.2% |
| Asian | 3.9% | 2.6% | 5.6% |
| Native American | 0.4% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.1% | 0.4% |
| Two or More Races | 6.5% | 1.5% | 3.2% |
| Hispanic | 6.9% | 4.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Decatur, GA | Tuscaloosa, AL | United States |
| Married Population | 58.3% | 34.3% | 49.8% |
| Currently Married | 56.7% | 32.6% | 48.0% |
| Married but Separated | 1.6% | 1.8% | 1.8% |
| Single Population | 41.7% | 65.7% | 50.2% |
| Never Married | 27.6% | 52.3% | 33.8% |
| Divorced | 9.6% | 9.4% | 10.8% |
| Widowed | 4.6% | 4.0% | 5.6% |
| space5 | | | |
| Household Size | 2.64 | 2.45 | 2.60 |
| Households | 8,906 | 36,763 | 124,010,992 |
| Family Households | 5,849 | 19,428 | 80,755,759 |
| Married couple, w/children | 52.8% | 25.2% | 30.5% |
| Married couple, no children | 31.0% | 39.5% | 42.9% |
| Non Family Households | 3,057 | 17,335 | 43,255,233 |
| Single householder, w/children | 12.1% | 22.3% | 15.8% |
| Single householder, no children | 4.2% | 12.9% | 10.8% |