| | Manchester-by-the-Sea, MA | Cohasset, MA | United States |
| Population | 5,382 | 8,295 | 329,725,481 |
| Female Population | 51.1% | 52.9% | 50.5% |
| Male Population | 48.9% | 47.1% | 49.5% |
| Median Age | 48 | 45.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 5,147 | 7,549 | 309,327,143 |
| Population - 2000 | 5,228 | 7,261 | 285,036,114 |
| Population - 1990 | 5,169 | 7,075 | 251,960,433 |
| Pop. 2000 to Now | 4.0% | 17.5% | 15.6% |
| Pop. 1990 to Now | 5.2% | 20.6% | 30.8% |
| space4 | | | |
| Population Density | 583.2 | 847.4 | 93.4 |
| Land Area | 9.2 | 9.8 | 3,531,905.4 |
| Water Area | 9.0 | 21.6 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Manchester-by-the-Sea, MA | Cohasset, MA | United States |
| Age 0 to 4 | 4.6% | 9.0% | 5.9% |
| Age 5 to 9 | 4.1% | 8.5% | 6.1% |
| Age 10 to 14 | 11.2% | 7.0% | 6.6% |
| Age 15 to 17 | 5.4% | 3.8% | 3.9% |
| Age 18 to 20 | 2.6% | 1.0% | 4.0% |
| Age 21 to 24 | 0.9% | 2.8% | 5.2% |
| Age 25 to 34 | 6.7% | 5.3% | 13.8% |
| Age 35 to 44 | 9.8% | 12.4% | 12.9% |
| Age 45 to 54 | 16.7% | 15.0% | 12.6% |
| Age 55 to 59 | 8.8% | 11.0% | 6.7% |
| Age 60 to 64 | 6.7% | 7.2% | 6.3% |
| Age 65 to 74 | 16.2% | 9.7% | 9.6% |
| Age 75 to 84 | 4.2% | 4.2% | 4.5% |
| Age 85 and over | 2.1% | 3.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Manchester-by-the-Sea, MA | Cohasset, MA | United States |
| White | 91.4% | 93.8% | 59.4% |
| Black | 0.0% | 1.0% | 12.2% |
| Asian | 1.1% | 0.4% | 5.6% |
| Native American | 0.0% | 0.4% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.4% | 0.2% |
| Other | 3.4% | 1.2% | 0.4% |
| Two or More Races | 2.4% | 1.7% | 3.2% |
| Hispanic | 1.8% | 1.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Manchester-by-the-Sea, MA | Cohasset, MA | United States |
| Married Population | 66.4% | 66.8% | 49.8% |
| Currently Married | 66.0% | 65.6% | 48.0% |
| Married but Separated | 0.4% | 1.2% | 1.8% |
| Single Population | 33.6% | 33.2% | 50.2% |
| Never Married | 19.5% | 19.7% | 33.8% |
| Divorced | 10.0% | 7.6% | 10.8% |
| Widowed | 4.1% | 5.9% | 5.6% |
| space5 | | | |
| Household Size | 2.58 | 2.61 | 2.60 |
| Households | 2,080 | 3,146 | 124,010,992 |
| Family Households | 1,488 | 2,230 | 80,755,759 |
| Married couple, w/children | 41.1% | 42.9% | 30.5% |
| Married couple, no children | 51.8% | 46.1% | 42.9% |
| Non Family Households | 592 | 916 | 43,255,233 |
| Single householder, w/children | 3.8% | 8.7% | 15.8% |
| Single householder, no children | 3.3% | 2.3% | 10.8% |