| | Bellevue, WA | South San Francisco, CA | United States |
| Population | 149,365 | 66,331 | 329,725,481 |
| Female Population | 48.4% | 49.8% | 50.5% |
| Male Population | 51.6% | 50.2% | 49.5% |
| Median Age | 37.9 | 42.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 128,360 | 63,674 | 309,327,143 |
| Population - 2000 | 109,569 | 60,552 | 285,036,114 |
| Population - 1990 | 86,874 | 54,312 | 251,960,433 |
| Pop. 2000 to Now | 35.1% | 9.9% | 15.6% |
| Pop. 1990 to Now | 70.5% | 22.6% | 30.8% |
| space4 | | | |
| Population Density | 4,464.0 | 7,189.6 | 93.4 |
| Land Area | 33.5 | 9.2 | 3,531,905.4 |
| Water Area | 0.3 | 21.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Bellevue, WA | South San Francisco, CA | United States |
| Age 0 to 4 | 5.5% | 4.6% | 5.9% |
| Age 5 to 9 | 5.6% | 5.4% | 6.1% |
| Age 10 to 14 | 5.9% | 4.9% | 6.6% |
| Age 15 to 17 | 3.5% | 2.8% | 3.9% |
| Age 18 to 20 | 2.5% | 3.1% | 4.0% |
| Age 21 to 24 | 3.8% | 4.4% | 5.2% |
| Age 25 to 34 | 18.6% | 14.4% | 13.8% |
| Age 35 to 44 | 14.8% | 14.1% | 12.9% |
| Age 45 to 54 | 14.0% | 14.8% | 12.6% |
| Age 55 to 59 | 6.6% | 7.6% | 6.7% |
| Age 60 to 64 | 5.0% | 7.2% | 6.3% |
| Age 65 to 74 | 7.6% | 10.1% | 9.6% |
| Age 75 to 84 | 3.9% | 4.4% | 4.5% |
| Age 85 and over | 2.7% | 2.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Bellevue, WA | South San Francisco, CA | United States |
| White | 46.1% | 21.5% | 59.4% |
| Black | 2.7% | 1.8% | 12.2% |
| Asian | 38.3% | 42.8% | 5.6% |
| Native American | 0.2% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.2% | 0.9% | 0.2% |
| Other | 0.6% | 0.2% | 0.4% |
| Two or More Races | 4.2% | 2.9% | 3.2% |
| Hispanic | 7.7% | 29.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Bellevue, WA | South San Francisco, CA | United States |
| Married Population | 59.3% | 53.3% | 49.8% |
| Currently Married | 58.3% | 51.9% | 48.0% |
| Married but Separated | 1.0% | 1.4% | 1.8% |
| Single Population | 40.7% | 46.7% | 50.2% |
| Never Married | 29.8% | 33.3% | 33.8% |
| Divorced | 7.3% | 8.0% | 10.8% |
| Widowed | 3.6% | 5.3% | 5.6% |
| space5 | | | |
| Household Size | 2.48 | 3.00 | 2.60 |
| Households | 59,800 | 21,895 | 124,010,992 |
| Family Households | 38,791 | 16,064 | 80,755,759 |
| Married couple, w/children | 40.5% | 31.7% | 30.5% |
| Married couple, no children | 45.9% | 43.8% | 42.9% |
| Non Family Households | 21,009 | 5,831 | 43,255,233 |
| Single householder, w/children | 6.5% | 8.9% | 15.8% |
| Single householder, no children | 7.1% | 15.6% | 10.8% |