| | Sullivan, WI | Hartford, VT | United States |
| Population | 666 | 10,604 | 329,725,481 |
| Female Population | 46.0% | 57.0% | 50.5% |
| Male Population | 54.1% | 43.0% | 49.5% |
| Median Age | 41.2 | 45.5 | 38.4 |
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| Population - 2010 | 667 | 9,931 | 309,327,143 |
| Population - 2000 | 688 | 10,367 | 285,036,114 |
| Population - 1990 | 432 | 9,404 | 251,960,433 |
| Pop. 2000 to Now | -3.2% | -7.7% | 15.6% |
| Pop. 1990 to Now | 54.2% | 1.7% | 30.8% |
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| Population Density | 587.8 | 235.6 | 93.4 |
| Land Area | 1.1 | 45.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.9 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Sullivan, WI | Hartford, VT | United States |
| Age 0 to 4 | 5.3% | 3.6% | 5.9% |
| Age 5 to 9 | 5.9% | 6.0% | 6.1% |
| Age 10 to 14 | 5.7% | 6.3% | 6.6% |
| Age 15 to 17 | 4.4% | 2.8% | 3.9% |
| Age 18 to 20 | 3.9% | 3.5% | 4.0% |
| Age 21 to 24 | 4.1% | 2.8% | 5.2% |
| Age 25 to 34 | 11.9% | 13.2% | 13.8% |
| Age 35 to 44 | 14.4% | 10.7% | 12.9% |
| Age 45 to 54 | 12.8% | 11.6% | 12.6% |
| Age 55 to 59 | 9.0% | 7.2% | 6.7% |
| Age 60 to 64 | 6.8% | 7.7% | 6.3% |
| Age 65 to 74 | 12.9% | 12.4% | 9.6% |
| Age 75 to 84 | 2.4% | 8.9% | 4.5% |
| Age 85 and over | 0.8% | 3.2% | 1.9% |
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| Race | | | |
| | Sullivan, WI | Hartford, VT | United States |
| White | 94.6% | 91.0% | 59.4% |
| Black | 0.0% | 0.8% | 12.2% |
| Asian | 0.0% | 2.6% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 1.1% | 2.5% | 3.2% |
| Hispanic | 4.4% | 2.7% | 18.4% |
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| Marriage & Family | | | |
| | Sullivan, WI | Hartford, VT | United States |
| Married Population | 50.4% | 49.0% | 49.8% |
| Currently Married | 50.4% | 47.7% | 48.0% |
| Married but Separated | 0.0% | 1.3% | 1.8% |
| Single Population | 49.6% | 51.0% | 50.2% |
| Never Married | 31.2% | 28.5% | 33.8% |
| Divorced | 14.3% | 14.0% | 10.8% |
| Widowed | 4.2% | 8.6% | 5.6% |
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| Household Size | 2.48 | 2.20 | 2.60 |
| Households | 269 | 4,765 | 124,010,992 |
| Family Households | 161 | 2,529 | 80,755,759 |
| Married couple, w/children | 29.8% | 27.2% | 30.5% |
| Married couple, no children | 46.0% | 50.5% | 42.9% |
| Non Family Households | 108 | 2,236 | 43,255,233 |
| Single householder, w/children | 13.0% | 12.6% | 15.8% |
| Single householder, no children | 11.2% | 9.8% | 10.8% |