| | Mill Creek East, WA | Rio Vista, CA | United States |
| Population | 25,528 | 9,850 | 329,725,481 |
| Female Population | 48.8% | 55.6% | 50.5% |
| Male Population | 51.2% | 44.4% | 49.5% |
| Median Age | 35 | 64 | 38.4 |
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| Population - 2010 | 14,058 | 7,374 | 309,327,143 |
| Population - 2000 | 10,648 | 4,571 | 285,036,114 |
| Population - 1990 | 8,972 | 3,316 | 251,960,433 |
| Pop. 2000 to Now | 107.8% | 118.3% | 15.6% |
| Pop. 1990 to Now | 146.6% | 200.9% | 30.8% |
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| Population Density | 5,719.9 | 1,484.3 | 93.4 |
| Land Area | 4.5 | 6.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.4 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Mill Creek East, WA | Rio Vista, CA | United States |
| Age 0 to 4 | 8.8% | 1.9% | 5.9% |
| Age 5 to 9 | 10.6% | 1.7% | 6.1% |
| Age 10 to 14 | 7.5% | 1.8% | 6.6% |
| Age 15 to 17 | 4.2% | 1.3% | 3.9% |
| Age 18 to 20 | 2.8% | 0.0% | 4.0% |
| Age 21 to 24 | 3.3% | 2.8% | 5.2% |
| Age 25 to 34 | 12.8% | 11.8% | 13.8% |
| Age 35 to 44 | 19.9% | 2.6% | 12.9% |
| Age 45 to 54 | 14.8% | 7.7% | 12.6% |
| Age 55 to 59 | 4.5% | 6.5% | 6.7% |
| Age 60 to 64 | 3.5% | 16.2% | 6.3% |
| Age 65 to 74 | 5.7% | 25.8% | 9.6% |
| Age 75 to 84 | 1.2% | 17.2% | 4.5% |
| Age 85 and over | 0.4% | 2.8% | 1.9% |
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| Race | | | |
| | Mill Creek East, WA | Rio Vista, CA | United States |
| White | 49.7% | 64.0% | 59.4% |
| Black | 2.4% | 12.4% | 12.2% |
| Asian | 34.2% | 4.5% | 5.6% |
| Native American | 1.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.3% | 0.2% |
| Other | 0.4% | 0.2% | 0.4% |
| Two or More Races | 4.4% | 1.4% | 3.2% |
| Hispanic | 7.9% | 17.3% | 18.4% |
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| Marriage & Family | | | |
| | Mill Creek East, WA | Rio Vista, CA | United States |
| Married Population | 69.8% | 54.3% | 49.8% |
| Currently Married | 68.8% | 51.4% | 48.0% |
| Married but Separated | 1.0% | 2.9% | 1.8% |
| Single Population | 30.2% | 45.7% | 50.2% |
| Never Married | 21.9% | 19.0% | 33.8% |
| Divorced | 7.3% | 16.9% | 10.8% |
| Widowed | 1.1% | 9.9% | 5.6% |
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| Household Size | 3.22 | 1.96 | 2.60 |
| Households | 7,909 | 5,025 | 124,010,992 |
| Family Households | 7,068 | 2,878 | 80,755,759 |
| Married couple, w/children | 57.3% | 6.9% | 30.5% |
| Married couple, no children | 30.8% | 70.0% | 42.9% |
| Non Family Households | 841 | 2,147 | 43,255,233 |
| Single householder, w/children | 6.9% | 5.9% | 15.8% |
| Single householder, no children | 4.9% | 17.1% | 10.8% |