| | South Yarmouth, MA | Chatham, MA | United States |
| Population | 11,696 | 6,554 | 329,725,481 |
| Female Population | 49.3% | 48.9% | 50.5% |
| Male Population | 50.7% | 51.1% | 49.5% |
| Median Age | 54.3 | 62.5 | 38.4 |
| space3 | | | |
| Population - 2010 | 11,468 | 6,119 | 309,327,143 |
| Population - 2000 | 11,603 | 6,625 | 285,036,114 |
| Population - 1990 | 10,358 | 6,579 | 251,960,433 |
| Pop. 2000 to Now | -2.2% | -9.5% | 15.6% |
| Pop. 1990 to Now | 9.5% | -8.9% | 30.8% |
| space4 | | | |
| Population Density | 1,681.4 | 406.3 | 93.4 |
| Land Area | 7.0 | 16.1 | 3,531,905.4 |
| Water Area | 0.9 | 8.3 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | South Yarmouth, MA | Chatham, MA | United States |
| Age 0 to 4 | 3.5% | 3.5% | 5.9% |
| Age 5 to 9 | 3.5% | 1.0% | 6.1% |
| Age 10 to 14 | 2.8% | 2.4% | 6.6% |
| Age 15 to 17 | 2.6% | 2.4% | 3.9% |
| Age 18 to 20 | 2.9% | 1.9% | 4.0% |
| Age 21 to 24 | 4.7% | 3.2% | 5.2% |
| Age 25 to 34 | 11.1% | 7.1% | 13.8% |
| Age 35 to 44 | 9.7% | 5.7% | 12.9% |
| Age 45 to 54 | 9.8% | 8.9% | 12.6% |
| Age 55 to 59 | 9.0% | 8.8% | 6.7% |
| Age 60 to 64 | 9.7% | 8.7% | 6.3% |
| Age 65 to 74 | 14.9% | 21.6% | 9.6% |
| Age 75 to 84 | 9.1% | 16.6% | 4.5% |
| Age 85 and over | 6.9% | 8.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | South Yarmouth, MA | Chatham, MA | United States |
| White | 81.3% | 95.1% | 59.4% |
| Black | 7.6% | 1.1% | 12.2% |
| Asian | 4.2% | 2.1% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 1.0% | 0.0% | 0.4% |
| Two or More Races | 2.8% | 0.5% | 3.2% |
| Hispanic | 3.2% | 1.3% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | South Yarmouth, MA | Chatham, MA | United States |
| Married Population | 48.0% | 59.2% | 49.8% |
| Currently Married | 47.6% | 58.9% | 48.0% |
| Married but Separated | 0.4% | 0.3% | 1.8% |
| Single Population | 52.0% | 40.8% | 50.2% |
| Never Married | 31.4% | 22.8% | 33.8% |
| Divorced | 11.6% | 8.5% | 10.8% |
| Widowed | 9.0% | 9.5% | 5.6% |
| space5 | | | |
| Household Size | 2.38 | 2.02 | 2.60 |
| Households | 4,846 | 3,164 | 124,010,992 |
| Family Households | 3,067 | 2,031 | 80,755,759 |
| Married couple, w/children | 8.9% | 11.0% | 30.5% |
| Married couple, no children | 58.4% | 76.1% | 42.9% |
| Non Family Households | 1,779 | 1,133 | 43,255,233 |
| Single householder, w/children | 12.3% | 4.5% | 15.8% |
| Single householder, no children | 20.4% | 8.4% | 10.8% |