| | Alstead, NH | New Milford, CT | United States |
| Population | 1,626 | 28,074 | 329,725,481 |
| Female Population | 54.8% | 53.0% | 50.5% |
| Male Population | 45.2% | 47.0% | 49.5% |
| Median Age | 50.8 | 42.7 | 38.4 |
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| Population - 2010 | 1,940 | 28,067 | 309,327,143 |
| Population - 2000 | 1,944 | 27,121 | 285,036,114 |
| Population - 1990 | 1,721 | 23,629 | 251,960,433 |
| Pop. 2000 to Now | 0.4% | -1.6% | 15.6% |
| Pop. 1990 to Now | 13.4% | 12.9% | 30.8% |
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| Population Density | 41.9 | 455.9 | 93.4 |
| Land Area | 38.8 | 61.6 | 3,531,905.4 |
| Water Area | 0.6 | 2.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Alstead, NH | New Milford, CT | United States |
| Age 0 to 4 | 3.3% | 5.7% | 5.9% |
| Age 5 to 9 | 3.6% | 5.8% | 6.1% |
| Age 10 to 14 | 4.3% | 5.4% | 6.6% |
| Age 15 to 17 | 3.0% | 4.6% | 3.9% |
| Age 18 to 20 | 1.7% | 3.6% | 4.0% |
| Age 21 to 24 | 1.4% | 3.9% | 5.2% |
| Age 25 to 34 | 15.7% | 11.9% | 13.8% |
| Age 35 to 44 | 8.4% | 11.7% | 12.9% |
| Age 45 to 54 | 13.5% | 14.5% | 12.6% |
| Age 55 to 59 | 10.0% | 7.9% | 6.7% |
| Age 60 to 64 | 10.2% | 9.5% | 6.3% |
| Age 65 to 74 | 17.0% | 10.0% | 9.6% |
| Age 75 to 84 | 7.3% | 4.2% | 4.5% |
| Age 85 and over | 0.6% | 1.4% | 1.9% |
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| Race | | | |
| | Alstead, NH | New Milford, CT | United States |
| White | 92.7% | 82.5% | 59.4% |
| Black | 0.0% | 2.4% | 12.2% |
| Asian | 0.7% | 2.9% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.1% | 0.4% |
| Two or More Races | 4.5% | 2.9% | 3.2% |
| Hispanic | 2.0% | 9.2% | 18.4% |
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| Marriage & Family | | | |
| | Alstead, NH | New Milford, CT | United States |
| Married Population | 54.3% | 55.4% | 49.8% |
| Currently Married | 52.6% | 54.5% | 48.0% |
| Married but Separated | 1.7% | 0.8% | 1.8% |
| Single Population | 45.7% | 44.6% | 50.2% |
| Never Married | 24.4% | 28.7% | 33.8% |
| Divorced | 17.9% | 11.1% | 10.8% |
| Widowed | 3.4% | 4.8% | 5.6% |
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| Household Size | 2.15 | 2.61 | 2.60 |
| Households | 757 | 10,656 | 124,010,992 |
| Family Households | 492 | 7,708 | 80,755,759 |
| Married couple, w/children | 13.8% | 30.9% | 30.5% |
| Married couple, no children | 64.6% | 48.5% | 42.9% |
| Non Family Households | 265 | 2,948 | 43,255,233 |
| Single householder, w/children | 13.4% | 12.5% | 15.8% |
| Single householder, no children | 8.1% | 8.0% | 10.8% |