| | Dennis, MA | Chestnut Ridge, NY | United States |
| Population | 14,664 | 10,211 | 329,725,481 |
| Female Population | 50.4% | 49.8% | 50.5% |
| Male Population | 49.6% | 50.2% | 49.5% |
| Median Age | 57.5 | 30.3 | 38.4 |
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| Population - 2010 | 14,220 | 7,937 | 309,327,143 |
| Population - 2000 | 15,973 | 7,829 | 285,036,114 |
| Population - 1990 | 13,864 | 7,517 | 251,960,433 |
| Pop. 2000 to Now | -13.0% | 2.1% | 15.6% |
| Pop. 1990 to Now | 0.2% | 6.4% | 30.8% |
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| Population Density | 715.0 | 2,062.0 | 93.4 |
| Land Area | 20.5 | 5.0 | 3,531,905.4 |
| Water Area | 1.8 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Dennis, MA | Chestnut Ridge, NY | United States |
| Age 0 to 4 | 3.3% | 13.4% | 5.9% |
| Age 5 to 9 | 2.8% | 12.0% | 6.1% |
| Age 10 to 14 | 2.9% | 8.7% | 6.6% |
| Age 15 to 17 | 2.1% | 2.4% | 3.9% |
| Age 18 to 20 | 2.0% | 2.3% | 4.0% |
| Age 21 to 24 | 4.8% | 2.4% | 5.2% |
| Age 25 to 34 | 8.1% | 16.5% | 13.8% |
| Age 35 to 44 | 8.4% | 7.5% | 12.9% |
| Age 45 to 54 | 11.9% | 9.3% | 12.6% |
| Age 55 to 59 | 9.6% | 6.6% | 6.7% |
| Age 60 to 64 | 9.1% | 3.4% | 6.3% |
| Age 65 to 74 | 19.9% | 8.2% | 9.6% |
| Age 75 to 84 | 11.0% | 4.2% | 4.5% |
| Age 85 and over | 4.1% | 3.2% | 1.9% |
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| Race | | | |
| | Dennis, MA | Chestnut Ridge, NY | United States |
| White | 89.4% | 69.4% | 59.4% |
| Black | 2.8% | 11.9% | 12.2% |
| Asian | 0.7% | 3.0% | 5.6% |
| Native American | 0.5% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.3% | 1.4% | 0.4% |
| Two or More Races | 1.8% | 4.0% | 3.2% |
| Hispanic | 4.3% | 10.3% | 18.4% |
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| Marriage & Family | | | |
| | Dennis, MA | Chestnut Ridge, NY | United States |
| Married Population | 51.3% | 62.1% | 49.8% |
| Currently Married | 50.7% | 60.6% | 48.0% |
| Married but Separated | 0.6% | 1.5% | 1.8% |
| Single Population | 48.7% | 37.9% | 50.2% |
| Never Married | 25.9% | 25.6% | 33.8% |
| Divorced | 14.3% | 6.7% | 10.8% |
| Widowed | 8.6% | 5.7% | 5.6% |
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| Household Size | 2.08 | 3.65 | 2.60 |
| Households | 6,989 | 2,751 | 124,010,992 |
| Family Households | 3,999 | 2,179 | 80,755,759 |
| Married couple, w/children | 12.4% | 47.0% | 30.5% |
| Married couple, no children | 61.0% | 40.5% | 42.9% |
| Non Family Households | 2,990 | 572 | 43,255,233 |
| Single householder, w/children | 13.1% | 4.6% | 15.8% |
| Single householder, no children | 13.6% | 7.8% | 10.8% |