| | Dennis, MA | Barrington, RI | United States |
| Population | 14,664 | 17,201 | 329,725,481 |
| Female Population | 50.4% | 52.6% | 50.5% |
| Male Population | 49.6% | 47.4% | 49.5% |
| Median Age | 57.5 | 43.5 | 38.4 |
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| Population - 2010 | 14,220 | 16,272 | 309,327,143 |
| Population - 2000 | 15,973 | 16,819 | 285,036,114 |
| Population - 1990 | 13,864 | 15,849 | 251,960,433 |
| Pop. 2000 to Now | -13.0% | -4.8% | 15.6% |
| Pop. 1990 to Now | 0.2% | 1.1% | 30.8% |
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| Population Density | 715.0 | 2,093.9 | 93.4 |
| Land Area | 20.5 | 8.2 | 3,531,905.4 |
| Water Area | 1.8 | 7.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Dennis, MA | Barrington, RI | United States |
| Age 0 to 4 | 3.3% | 6.0% | 5.9% |
| Age 5 to 9 | 2.8% | 7.5% | 6.1% |
| Age 10 to 14 | 2.9% | 8.4% | 6.6% |
| Age 15 to 17 | 2.1% | 6.0% | 3.9% |
| Age 18 to 20 | 2.0% | 1.5% | 4.0% |
| Age 21 to 24 | 4.8% | 2.1% | 5.2% |
| Age 25 to 34 | 8.1% | 7.6% | 13.8% |
| Age 35 to 44 | 8.4% | 13.6% | 12.9% |
| Age 45 to 54 | 11.9% | 17.3% | 12.6% |
| Age 55 to 59 | 9.6% | 7.8% | 6.7% |
| Age 60 to 64 | 9.1% | 6.9% | 6.3% |
| Age 65 to 74 | 19.9% | 8.5% | 9.6% |
| Age 75 to 84 | 11.0% | 5.2% | 4.5% |
| Age 85 and over | 4.1% | 1.7% | 1.9% |
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| Race | | | |
| | Dennis, MA | Barrington, RI | United States |
| White | 89.4% | 88.3% | 59.4% |
| Black | 2.8% | 0.3% | 12.2% |
| Asian | 0.7% | 4.4% | 5.6% |
| Native American | 0.5% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.3% | 0.2% | 0.4% |
| Two or More Races | 1.8% | 2.2% | 3.2% |
| Hispanic | 4.3% | 4.5% | 18.4% |
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| Marriage & Family | | | |
| | Dennis, MA | Barrington, RI | United States |
| Married Population | 51.3% | 64.0% | 49.8% |
| Currently Married | 50.7% | 62.7% | 48.0% |
| Married but Separated | 0.6% | 1.3% | 1.8% |
| Single Population | 48.7% | 36.0% | 50.2% |
| Never Married | 25.9% | 23.3% | 33.8% |
| Divorced | 14.3% | 8.9% | 10.8% |
| Widowed | 8.6% | 3.8% | 5.6% |
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| Household Size | 2.08 | 2.78 | 2.60 |
| Households | 6,989 | 6,176 | 124,010,992 |
| Family Households | 3,999 | 4,937 | 80,755,759 |
| Married couple, w/children | 12.4% | 44.2% | 30.5% |
| Married couple, no children | 61.0% | 39.1% | 42.9% |
| Non Family Households | 2,990 | 1,239 | 43,255,233 |
| Single householder, w/children | 13.1% | 10.7% | 15.8% |
| Single householder, no children | 13.6% | 6.0% | 10.8% |