| | Sidney, ME | Yarmouth, ME | United States |
| Population | 4,615 | 8,903 | 329,725,481 |
| Female Population | 51.6% | 54.4% | 50.5% |
| Male Population | 48.5% | 45.6% | 49.5% |
| Median Age | 37.8 | 44.8 | 38.4 |
| space3 | | | |
| Population - 2010 | 4,231 | 8,344 | 309,327,143 |
| Population - 2000 | 3,514 | 8,360 | 285,036,114 |
| Population - 1990 | 2,593 | 7,862 | 251,960,433 |
| Pop. 2000 to Now | 29.3% | 2.9% | 15.6% |
| Pop. 1990 to Now | 75.2% | 9.4% | 30.8% |
| space4 | | | |
| Population Density | 109.2 | 666.8 | 93.4 |
| Land Area | 42.2 | 13.4 | 3,531,905.4 |
| Water Area | 3.3 | 9.6 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Sidney, ME | Yarmouth, ME | United States |
| Age 0 to 4 | 6.3% | 3.2% | 5.9% |
| Age 5 to 9 | 5.0% | 5.8% | 6.1% |
| Age 10 to 14 | 7.7% | 7.1% | 6.6% |
| Age 15 to 17 | 3.2% | 8.3% | 3.9% |
| Age 18 to 20 | 4.1% | 2.7% | 4.0% |
| Age 21 to 24 | 4.9% | 3.2% | 5.2% |
| Age 25 to 34 | 11.1% | 10.1% | 13.8% |
| Age 35 to 44 | 14.5% | 9.7% | 12.9% |
| Age 45 to 54 | 11.9% | 15.7% | 12.6% |
| Age 55 to 59 | 10.0% | 9.1% | 6.7% |
| Age 60 to 64 | 5.6% | 6.5% | 6.3% |
| Age 65 to 74 | 12.0% | 9.6% | 9.6% |
| Age 75 to 84 | 4.0% | 6.1% | 4.5% |
| Age 85 and over | 0.0% | 2.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Sidney, ME | Yarmouth, ME | United States |
| White | 98.5% | 92.9% | 59.4% |
| Black | 0.0% | 0.5% | 12.2% |
| Asian | 0.0% | 2.7% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 2.0% | 0.4% |
| Two or More Races | 0.5% | 0.3% | 3.2% |
| Hispanic | 1.0% | 1.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Sidney, ME | Yarmouth, ME | United States |
| Married Population | 57.5% | 45.5% | 49.8% |
| Currently Married | 57.5% | 44.9% | 48.0% |
| Married but Separated | 0.0% | 0.6% | 1.8% |
| Single Population | 42.5% | 54.5% | 50.2% |
| Never Married | 23.3% | 30.2% | 33.8% |
| Divorced | 15.8% | 17.1% | 10.8% |
| Widowed | 3.4% | 7.2% | 5.6% |
| space5 | | | |
| Household Size | 2.44 | 2.53 | 2.60 |
| Households | 1,888 | 3,463 | 124,010,992 |
| Family Households | 1,480 | 2,353 | 80,755,759 |
| Married couple, w/children | 23.1% | 30.5% | 30.5% |
| Married couple, no children | 50.5% | 39.3% | 42.9% |
| Non Family Households | 408 | 1,110 | 43,255,233 |
| Single householder, w/children | 20.9% | 21.1% | 15.8% |
| Single householder, no children | 5.4% | 9.2% | 10.8% |