| | Oak Park, CA | Napa, CA | United States |
| Population | 13,561 | 79,700 | 329,725,481 |
| Female Population | 52.0% | 50.3% | 50.5% |
| Male Population | 48.0% | 49.7% | 49.5% |
| Median Age | 42.9 | 39.9 | 38.4 |
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| Population - 2010 | 14,044 | 77,187 | 309,327,143 |
| Population - 2000 | 2,320 | 72,585 | 285,036,114 |
| Population - 1990 | 2,412 | 61,842 | 251,960,433 |
| Pop. 2000 to Now | 519.3% | 6.1% | 15.6% |
| Pop. 1990 to Now | 495.7% | 24.6% | 30.8% |
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| Population Density | 2,561.6 | 4,439.9 | 93.4 |
| Land Area | 5.3 | 18.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.3 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Oak Park, CA | Napa, CA | United States |
| Age 0 to 4 | 6.2% | 5.4% | 5.9% |
| Age 5 to 9 | 5.3% | 5.4% | 6.1% |
| Age 10 to 14 | 8.4% | 6.8% | 6.6% |
| Age 15 to 17 | 5.3% | 4.0% | 3.9% |
| Age 18 to 20 | 3.2% | 3.4% | 4.0% |
| Age 21 to 24 | 3.8% | 4.7% | 5.2% |
| Age 25 to 34 | 6.6% | 13.6% | 13.8% |
| Age 35 to 44 | 13.7% | 13.5% | 12.9% |
| Age 45 to 54 | 15.6% | 13.2% | 12.6% |
| Age 55 to 59 | 10.1% | 6.5% | 6.7% |
| Age 60 to 64 | 6.2% | 6.1% | 6.3% |
| Age 65 to 74 | 10.4% | 10.4% | 9.6% |
| Age 75 to 84 | 2.6% | 5.0% | 4.5% |
| Age 85 and over | 2.4% | 2.1% | 1.9% |
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| Race | | | |
| | Oak Park, CA | Napa, CA | United States |
| White | 69.1% | 53.0% | 59.4% |
| Black | 0.9% | 0.6% | 12.2% |
| Asian | 17.7% | 2.9% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.1% | 0.2% |
| Other | 0.5% | 0.4% | 0.4% |
| Two or More Races | 3.2% | 3.2% | 3.2% |
| Hispanic | 8.5% | 39.6% | 18.4% |
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| Marriage & Family | | | |
| | Oak Park, CA | Napa, CA | United States |
| Married Population | 59.5% | 51.2% | 49.8% |
| Currently Married | 58.8% | 49.8% | 48.0% |
| Married but Separated | 0.6% | 1.4% | 1.8% |
| Single Population | 40.5% | 48.8% | 50.2% |
| Never Married | 25.6% | 32.2% | 33.8% |
| Divorced | 9.8% | 11.1% | 10.8% |
| Widowed | 5.1% | 5.5% | 5.6% |
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| Household Size | 2.70 | 2.71 | 2.60 |
| Households | 5,018 | 29,099 | 124,010,992 |
| Family Households | 3,478 | 19,393 | 80,755,759 |
| Married couple, w/children | 45.8% | 32.1% | 30.5% |
| Married couple, no children | 43.5% | 44.4% | 42.9% |
| Non Family Households | 1,540 | 9,706 | 43,255,233 |
| Single householder, w/children | 5.0% | 13.6% | 15.8% |
| Single householder, no children | 5.7% | 9.9% | 10.8% |