| | Louisville, CO | Aliso Viejo, CA | United States |
| Population | 21,091 | 51,943 | 329,725,481 |
| Female Population | 49.4% | 52.3% | 50.5% |
| Male Population | 50.6% | 47.7% | 49.5% |
| Median Age | 42.5 | 37.4 | 38.4 |
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| Population - 2010 | 18,412 | 47,821 | 309,327,143 |
| Population - 2000 | 18,937 | 40,166 | 285,036,114 |
| Population - 1990 | 12,361 | 7,612 | 251,960,433 |
| Pop. 2000 to Now | 0.7% | 25.5% | 15.6% |
| Pop. 1990 to Now | 54.2% | 562.3% | 30.8% |
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| Population Density | 2,644.0 | 7,507.3 | 93.4 |
| Land Area | 8.0 | 6.9 | 3,531,905.4 |
| Water Area | 0.1 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Louisville, CO | Aliso Viejo, CA | United States |
| Age 0 to 4 | 4.5% | 7.8% | 5.9% |
| Age 5 to 9 | 6.8% | 6.9% | 6.1% |
| Age 10 to 14 | 8.0% | 6.8% | 6.6% |
| Age 15 to 17 | 4.3% | 4.3% | 3.9% |
| Age 18 to 20 | 2.8% | 3.3% | 4.0% |
| Age 21 to 24 | 3.4% | 4.1% | 5.2% |
| Age 25 to 34 | 11.2% | 13.0% | 13.8% |
| Age 35 to 44 | 13.0% | 16.2% | 12.9% |
| Age 45 to 54 | 15.1% | 16.3% | 12.6% |
| Age 55 to 59 | 8.6% | 7.3% | 6.7% |
| Age 60 to 64 | 8.0% | 5.3% | 6.3% |
| Age 65 to 74 | 9.0% | 4.9% | 9.6% |
| Age 75 to 84 | 3.0% | 2.4% | 4.5% |
| Age 85 and over | 2.3% | 1.4% | 1.9% |
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| Race | | | |
| | Louisville, CO | Aliso Viejo, CA | United States |
| White | 82.3% | 56.1% | 59.4% |
| Black | 0.6% | 2.5% | 12.2% |
| Asian | 4.1% | 15.4% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.4% | 0.4% |
| Two or More Races | 4.0% | 5.3% | 3.2% |
| Hispanic | 8.8% | 20.0% | 18.4% |
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| Marriage & Family | | | |
| | Louisville, CO | Aliso Viejo, CA | United States |
| Married Population | 56.9% | 53.7% | 49.8% |
| Currently Married | 56.6% | 52.9% | 48.0% |
| Married but Separated | 0.3% | 0.9% | 1.8% |
| Single Population | 43.1% | 46.3% | 50.2% |
| Never Married | 27.8% | 31.3% | 33.8% |
| Divorced | 10.9% | 11.4% | 10.8% |
| Widowed | 4.4% | 3.6% | 5.6% |
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| Household Size | 2.50 | 2.71 | 2.60 |
| Households | 8,400 | 18,999 | 124,010,992 |
| Family Households | 5,519 | 13,033 | 80,755,759 |
| Married couple, w/children | 38.7% | 45.7% | 30.5% |
| Married couple, no children | 43.2% | 32.8% | 42.9% |
| Non Family Households | 2,881 | 5,966 | 43,255,233 |
| Single householder, w/children | 12.2% | 10.3% | 15.8% |
| Single householder, no children | 5.9% | 11.3% | 10.8% |