| | Fort Collins, CO | Auburn, CA | United States |
| Population | 166,788 | 13,738 | 329,725,481 |
| Female Population | 49.4% | 53.4% | 50.5% |
| Male Population | 50.6% | 46.6% | 49.5% |
| Median Age | 30 | 48.2 | 38.4 |
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| Population - 2010 | 145,123 | 13,349 | 309,327,143 |
| Population - 2000 | 118,652 | 12,462 | 285,036,114 |
| Population - 1990 | 87,758 | 10,592 | 251,960,433 |
| Pop. 2000 to Now | 41.8% | 14.0% | 15.6% |
| Pop. 1990 to Now | 91.7% | 34.1% | 30.8% |
| space4 | | | |
| Population Density | 2,941.6 | 1,914.2 | 93.4 |
| Land Area | 56.7 | 7.2 | 3,531,905.4 |
| Water Area | 1.3 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Fort Collins, CO | Auburn, CA | United States |
| Age 0 to 4 | 4.1% | 3.3% | 5.9% |
| Age 5 to 9 | 5.0% | 6.6% | 6.1% |
| Age 10 to 14 | 5.3% | 4.0% | 6.6% |
| Age 15 to 17 | 3.1% | 3.4% | 3.9% |
| Age 18 to 20 | 9.5% | 3.1% | 4.0% |
| Age 21 to 24 | 12.5% | 4.0% | 5.2% |
| Age 25 to 34 | 18.2% | 8.6% | 13.8% |
| Age 35 to 44 | 11.9% | 12.5% | 12.9% |
| Age 45 to 54 | 9.4% | 12.7% | 12.6% |
| Age 55 to 59 | 5.1% | 8.3% | 6.7% |
| Age 60 to 64 | 4.8% | 9.4% | 6.3% |
| Age 65 to 74 | 6.7% | 14.3% | 9.6% |
| Age 75 to 84 | 3.0% | 8.0% | 4.5% |
| Age 85 and over | 1.4% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Fort Collins, CO | Auburn, CA | United States |
| White | 78.1% | 80.6% | 59.4% |
| Black | 1.3% | 0.5% | 12.2% |
| Asian | 3.2% | 1.6% | 5.6% |
| Native American | 0.6% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.5% | 0.2% |
| Other | 0.4% | 0.3% | 0.4% |
| Two or More Races | 3.7% | 3.6% | 3.2% |
| Hispanic | 12.6% | 12.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Fort Collins, CO | Auburn, CA | United States |
| Married Population | 41.6% | 52.6% | 49.8% |
| Currently Married | 40.9% | 50.3% | 48.0% |
| Married but Separated | 0.7% | 2.4% | 1.8% |
| Single Population | 58.4% | 47.4% | 50.2% |
| Never Married | 46.6% | 25.6% | 33.8% |
| Divorced | 8.5% | 16.2% | 10.8% |
| Widowed | 3.3% | 5.5% | 5.6% |
| space5 | | | |
| Household Size | 2.36 | 2.15 | 2.60 |
| Households | 67,270 | 6,236 | 124,010,992 |
| Family Households | 35,069 | 3,621 | 80,755,759 |
| Married couple, w/children | 33.6% | 21.6% | 30.5% |
| Married couple, no children | 46.3% | 54.7% | 42.9% |
| Non Family Households | 32,201 | 2,615 | 43,255,233 |
| Single householder, w/children | 12.1% | 12.1% | 15.8% |
| Single householder, no children | 8.0% | 11.6% | 10.8% |