| | Cohasset, MA | Chevy Chase, MD | United States |
| Population | 8,295 | 2,913 | 329,725,481 |
| Female Population | 52.9% | 48.6% | 50.5% |
| Male Population | 47.1% | 51.4% | 49.5% |
| Median Age | 45.1 | 48.6 | 38.4 |
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| Population - 2010 | 7,549 | 2,834 | 309,327,143 |
| Population - 2000 | 7,261 | 2,726 | 285,036,114 |
| Population - 1990 | 7,075 | 2,675 | 251,960,433 |
| Pop. 2000 to Now | 17.5% | 9.3% | 15.6% |
| Pop. 1990 to Now | 20.6% | 11.4% | 30.8% |
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| Population Density | 847.4 | 6,264.5 | 93.4 |
| Land Area | 9.8 | 0.5 | 3,531,905.4 |
| Water Area | 21.6 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Cohasset, MA | Chevy Chase, MD | United States |
| Age 0 to 4 | 9.0% | 6.0% | 5.9% |
| Age 5 to 9 | 8.5% | 5.9% | 6.1% |
| Age 10 to 14 | 7.0% | 7.2% | 6.6% |
| Age 15 to 17 | 3.8% | 6.8% | 3.9% |
| Age 18 to 20 | 1.0% | 4.3% | 4.0% |
| Age 21 to 24 | 2.8% | 1.5% | 5.2% |
| Age 25 to 34 | 5.3% | 4.5% | 13.8% |
| Age 35 to 44 | 12.4% | 9.4% | 12.9% |
| Age 45 to 54 | 15.0% | 15.8% | 12.6% |
| Age 55 to 59 | 11.0% | 10.1% | 6.7% |
| Age 60 to 64 | 7.2% | 7.1% | 6.3% |
| Age 65 to 74 | 9.7% | 15.6% | 9.6% |
| Age 75 to 84 | 4.2% | 4.8% | 4.5% |
| Age 85 and over | 3.2% | 1.1% | 1.9% |
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| Race | | | |
| | Cohasset, MA | Chevy Chase, MD | United States |
| White | 93.8% | 84.0% | 59.4% |
| Black | 1.0% | 0.9% | 12.2% |
| Asian | 0.4% | 4.3% | 5.6% |
| Native American | 0.4% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.4% | 0.0% | 0.2% |
| Other | 1.2% | 1.1% | 0.4% |
| Two or More Races | 1.7% | 6.4% | 3.2% |
| Hispanic | 1.2% | 3.0% | 18.4% |
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| Marriage & Family | | | |
| | Cohasset, MA | Chevy Chase, MD | United States |
| Married Population | 66.8% | 73.1% | 49.8% |
| Currently Married | 65.6% | 72.3% | 48.0% |
| Married but Separated | 1.2% | 0.8% | 1.8% |
| Single Population | 33.2% | 26.9% | 50.2% |
| Never Married | 19.7% | 19.1% | 33.8% |
| Divorced | 7.6% | 4.2% | 10.8% |
| Widowed | 5.9% | 3.7% | 5.6% |
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| Household Size | 2.61 | 2.97 | 2.60 |
| Households | 3,146 | 981 | 124,010,992 |
| Family Households | 2,230 | 834 | 80,755,759 |
| Married couple, w/children | 42.9% | 42.9% | 30.5% |
| Married couple, no children | 46.1% | 51.9% | 42.9% |
| Non Family Households | 916 | 147 | 43,255,233 |
| Single householder, w/children | 8.7% | 3.7% | 15.8% |
| Single householder, no children | 2.3% | 1.4% | 10.8% |