| | Atascadero, CA | Indianapolis, IN | United States |
| Population | 29,771 | 880,104 | 329,725,481 |
| Female Population | 50.1% | 51.5% | 50.5% |
| Male Population | 49.9% | 48.5% | 49.5% |
| Median Age | 40 | 34.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 28,425 | 821,576 | 309,327,143 |
| Population - 2000 | 26,411 | 781,870 | 285,036,114 |
| Population - 1990 | 23,138 | 754,005 | 251,960,433 |
| Pop. 2000 to Now | 14.6% | 12.3% | 15.6% |
| Pop. 1990 to Now | 30.8% | 16.4% | 30.8% |
| space4 | | | |
| Population Density | 1,141.3 | 2,434.0 | 93.4 |
| Land Area | 26.1 | 361.6 | 3,531,905.4 |
| Water Area | 0.0 | 6.5 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Atascadero, CA | Indianapolis, IN | United States |
| Age 0 to 4 | 5.7% | 7.1% | 5.9% |
| Age 5 to 9 | 5.5% | 6.8% | 6.1% |
| Age 10 to 14 | 5.8% | 6.9% | 6.6% |
| Age 15 to 17 | 3.3% | 3.9% | 3.9% |
| Age 18 to 20 | 2.7% | 3.9% | 4.0% |
| Age 21 to 24 | 5.9% | 5.6% | 5.2% |
| Age 25 to 34 | 13.9% | 16.8% | 13.8% |
| Age 35 to 44 | 11.9% | 13.0% | 12.9% |
| Age 45 to 54 | 12.6% | 11.6% | 12.6% |
| Age 55 to 59 | 7.3% | 6.1% | 6.7% |
| Age 60 to 64 | 8.4% | 5.8% | 6.3% |
| Age 65 to 74 | 10.5% | 7.7% | 9.6% |
| Age 75 to 84 | 5.2% | 3.3% | 4.5% |
| Age 85 and over | 1.3% | 1.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Atascadero, CA | Indianapolis, IN | United States |
| White | 74.3% | 52.7% | 59.4% |
| Black | 0.6% | 28.5% | 12.2% |
| Asian | 1.6% | 3.8% | 5.6% |
| Native American | 0.4% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.5% | 0.5% | 0.4% |
| Two or More Races | 4.3% | 3.7% | 3.2% |
| Hispanic | 18.3% | 10.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Atascadero, CA | Indianapolis, IN | United States |
| Married Population | 54.8% | 41.1% | 49.8% |
| Currently Married | 53.1% | 39.4% | 48.0% |
| Married but Separated | 1.7% | 1.7% | 1.8% |
| Single Population | 45.2% | 58.9% | 50.2% |
| Never Married | 29.9% | 41.8% | 33.8% |
| Divorced | 10.7% | 12.3% | 10.8% |
| Widowed | 4.6% | 4.8% | 5.6% |
| space5 | | | |
| Household Size | 2.51 | 2.46 | 2.60 |
| Households | 11,733 | 352,238 | 124,010,992 |
| Family Households | 8,042 | 193,246 | 80,755,759 |
| Married couple, w/children | 29.3% | 26.6% | 30.5% |
| Married couple, no children | 47.9% | 38.7% | 42.9% |
| Non Family Households | 3,691 | 158,992 | 43,255,233 |
| Single householder, w/children | 12.0% | 22.4% | 15.8% |
| Single householder, no children | 10.7% | 12.4% | 10.8% |