| | Sullivan, IN | Lowell, IN | United States |
| Population | 4,238 | 10,569 | 329,725,481 |
| Female Population | 53.4% | 51.8% | 50.5% |
| Male Population | 46.6% | 48.2% | 49.5% |
| Median Age | 36.1 | 37.5 | 38.4 |
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| Population - 2010 | 4,215 | 9,314 | 309,327,143 |
| Population - 2000 | 4,617 | 7,505 | 285,036,114 |
| Population - 1990 | 4,663 | 6,430 | 251,960,433 |
| Pop. 2000 to Now | -11.4% | 35.1% | 15.6% |
| Pop. 1990 to Now | -12.3% | 57.7% | 30.8% |
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| Population Density | 2,259.1 | 1,727.5 | 93.4 |
| Land Area | 1.9 | 6.1 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Sullivan, IN | Lowell, IN | United States |
| Age 0 to 4 | 11.9% | 8.1% | 5.9% |
| Age 5 to 9 | 8.1% | 6.5% | 6.1% |
| Age 10 to 14 | 3.7% | 7.9% | 6.6% |
| Age 15 to 17 | 3.8% | 5.9% | 3.9% |
| Age 18 to 20 | 3.0% | 2.2% | 4.0% |
| Age 21 to 24 | 5.4% | 3.9% | 5.2% |
| Age 25 to 34 | 12.6% | 13.4% | 13.8% |
| Age 35 to 44 | 14.0% | 12.0% | 12.9% |
| Age 45 to 54 | 6.5% | 11.5% | 12.6% |
| Age 55 to 59 | 4.2% | 4.1% | 6.7% |
| Age 60 to 64 | 8.7% | 4.2% | 6.3% |
| Age 65 to 74 | 7.7% | 15.6% | 9.6% |
| Age 75 to 84 | 6.6% | 3.6% | 4.5% |
| Age 85 and over | 3.9% | 1.1% | 1.9% |
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| Race | | | |
| | Sullivan, IN | Lowell, IN | United States |
| White | 93.1% | 86.9% | 59.4% |
| Black | 0.1% | 0.2% | 12.2% |
| Asian | 0.4% | 0.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 6.4% | 0.7% | 3.2% |
| Hispanic | 0.0% | 12.0% | 18.4% |
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| Marriage & Family | | | |
| | Sullivan, IN | Lowell, IN | United States |
| Married Population | 39.4% | 58.8% | 49.8% |
| Currently Married | 37.8% | 57.2% | 48.0% |
| Married but Separated | 1.6% | 1.5% | 1.8% |
| Single Population | 60.6% | 41.2% | 50.2% |
| Never Married | 28.4% | 26.9% | 33.8% |
| Divorced | 16.4% | 6.6% | 10.8% |
| Widowed | 15.9% | 7.7% | 5.6% |
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| Household Size | 2.44 | 2.63 | 2.60 |
| Households | 1,706 | 3,982 | 124,010,992 |
| Family Households | 1,084 | 2,837 | 80,755,759 |
| Married couple, w/children | 23.8% | 42.8% | 30.5% |
| Married couple, no children | 31.6% | 37.3% | 42.9% |
| Non Family Households | 622 | 1,145 | 43,255,233 |
| Single householder, w/children | 30.4% | 11.2% | 15.8% |
| Single householder, no children | 14.3% | 8.7% | 10.8% |