| | Janesville, CA | Columbia, KY | United States |
| Population | 2,874 | 4,936 | 329,725,481 |
| Female Population | 53.0% | 49.5% | 50.5% |
| Male Population | 47.0% | 50.5% | 49.5% |
| Median Age | 51.3 | 25.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,204 | 4,572 | 309,327,143 |
| Population - 2000 | 1,357 | 4,014 | 285,036,114 |
| Population - 1990 | 1,115 | 3,845 | 251,960,433 |
| Pop. 2000 to Now | -8.1% | 22.1% | 15.6% |
| Pop. 1990 to Now | 11.8% | 27.5% | 30.8% |
| space4 | | | |
| Population Density | 217.9 | 1,019.2 | 93.4 |
| Land Area | 13.2 | 4.8 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Janesville, CA | Columbia, KY | United States |
| Age 0 to 4 | 5.4% | 5.8% | 5.9% |
| Age 5 to 9 | 4.5% | 4.9% | 6.1% |
| Age 10 to 14 | 5.2% | 4.7% | 6.6% |
| Age 15 to 17 | 0.3% | 4.0% | 3.9% |
| Age 18 to 20 | 4.6% | 18.9% | 4.0% |
| Age 21 to 24 | 0.8% | 11.5% | 5.2% |
| Age 25 to 34 | 11.6% | 8.4% | 13.8% |
| Age 35 to 44 | 7.4% | 11.2% | 12.9% |
| Age 45 to 54 | 19.9% | 7.2% | 12.6% |
| Age 55 to 59 | 12.5% | 3.5% | 6.7% |
| Age 60 to 64 | 5.9% | 5.8% | 6.3% |
| Age 65 to 74 | 9.9% | 6.9% | 9.6% |
| Age 75 to 84 | 9.5% | 4.5% | 4.5% |
| Age 85 and over | 2.4% | 2.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Janesville, CA | Columbia, KY | United States |
| White | 76.8% | 86.4% | 59.4% |
| Black | 0.0% | 4.3% | 12.2% |
| Asian | 1.2% | 0.4% | 5.6% |
| Native American | 2.9% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.2% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 4.0% | 3.0% | 3.2% |
| Hispanic | 15.1% | 5.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Janesville, CA | Columbia, KY | United States |
| Married Population | 68.4% | 34.0% | 49.8% |
| Currently Married | 66.2% | 31.7% | 48.0% |
| Married but Separated | 2.2% | 2.2% | 1.8% |
| Single Population | 31.6% | 66.0% | 50.2% |
| Never Married | 21.2% | 47.9% | 33.8% |
| Divorced | 5.2% | 10.4% | 10.8% |
| Widowed | 5.1% | 7.7% | 5.6% |
| space5 | | | |
| Household Size | 2.50 | 2.30 | 2.60 |
| Households | 1,146 | 1,580 | 124,010,992 |
| Family Households | 958 | 943 | 80,755,759 |
| Married couple, w/children | 7.6% | 29.9% | 30.5% |
| Married couple, no children | 76.4% | 37.8% | 42.9% |
| Non Family Households | 188 | 637 | 43,255,233 |
| Single householder, w/children | 9.1% | 20.9% | 15.8% |
| Single householder, no children | 6.9% | 11.5% | 10.8% |