| | Waterville, ME | Sebastopol, CA | United States |
| Population | 15,872 | 7,563 | 329,725,481 |
| Female Population | 52.7% | 53.8% | 50.5% |
| Male Population | 47.3% | 46.3% | 49.5% |
| Median Age | 35.7 | 49.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 15,727 | 7,474 | 309,327,143 |
| Population - 2000 | 15,605 | 7,774 | 285,036,114 |
| Population - 1990 | 17,173 | 7,004 | 251,960,433 |
| Pop. 2000 to Now | 6.2% | -2.3% | 15.6% |
| Pop. 1990 to Now | -3.5% | 8.4% | 30.8% |
| space4 | | | |
| Population Density | 1,172.9 | 4,066.1 | 93.4 |
| Land Area | 13.5 | 1.9 | 3,531,905.4 |
| Water Area | 0.5 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Waterville, ME | Sebastopol, CA | United States |
| Age 0 to 4 | 4.2% | 3.4% | 5.9% |
| Age 5 to 9 | 6.1% | 4.0% | 6.1% |
| Age 10 to 14 | 6.5% | 5.5% | 6.6% |
| Age 15 to 17 | 1.9% | 2.3% | 3.9% |
| Age 18 to 20 | 10.1% | 2.9% | 4.0% |
| Age 21 to 24 | 9.8% | 5.4% | 5.2% |
| Age 25 to 34 | 10.3% | 12.3% | 13.8% |
| Age 35 to 44 | 12.1% | 9.6% | 12.9% |
| Age 45 to 54 | 7.8% | 13.3% | 12.6% |
| Age 55 to 59 | 7.9% | 7.1% | 6.7% |
| Age 60 to 64 | 6.2% | 9.4% | 6.3% |
| Age 65 to 74 | 9.0% | 17.8% | 9.6% |
| Age 75 to 84 | 5.1% | 4.5% | 4.5% |
| Age 85 and over | 3.1% | 2.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Waterville, ME | Sebastopol, CA | United States |
| White | 88.9% | 72.0% | 59.4% |
| Black | 0.8% | 2.3% | 12.2% |
| Asian | 3.3% | 4.4% | 5.6% |
| Native American | 0.6% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.2% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 3.4% | 6.4% | 3.2% |
| Hispanic | 3.0% | 14.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Waterville, ME | Sebastopol, CA | United States |
| Married Population | 36.1% | 49.7% | 49.8% |
| Currently Married | 34.2% | 48.7% | 48.0% |
| Married but Separated | 1.9% | 1.0% | 1.8% |
| Single Population | 63.9% | 50.3% | 50.2% |
| Never Married | 43.7% | 29.1% | 33.8% |
| Divorced | 13.6% | 17.0% | 10.8% |
| Widowed | 6.6% | 4.3% | 5.6% |
| space5 | | | |
| Household Size | 2.13 | 2.32 | 2.60 |
| Households | 6,403 | 3,221 | 124,010,992 |
| Family Households | 3,285 | 1,927 | 80,755,759 |
| Married couple, w/children | 20.2% | 30.6% | 30.5% |
| Married couple, no children | 43.7% | 46.1% | 42.9% |
| Non Family Households | 3,118 | 1,294 | 43,255,233 |
| Single householder, w/children | 26.9% | 8.1% | 15.8% |
| Single householder, no children | 9.3% | 15.2% | 10.8% |