| | Selma, CA | Downey, CA | United States |
| Population | 24,545 | 114,293 | 329,725,481 |
| Female Population | 49.3% | 51.6% | 50.5% |
| Male Population | 50.7% | 48.4% | 49.5% |
| Median Age | 30.8 | 35.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 23,367 | 111,766 | 309,327,143 |
| Population - 2000 | 19,444 | 107,323 | 285,036,114 |
| Population - 1990 | 14,757 | 91,444 | 251,960,433 |
| Pop. 2000 to Now | 25.3% | 1.8% | 15.6% |
| Pop. 1990 to Now | 65.1% | 19.4% | 30.8% |
| space4 | | | |
| Population Density | 4,755.9 | 9,211.2 | 93.4 |
| Land Area | 5.2 | 12.4 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Selma, CA | Downey, CA | United States |
| Age 0 to 4 | 7.2% | 5.6% | 5.9% |
| Age 5 to 9 | 9.2% | 6.5% | 6.1% |
| Age 10 to 14 | 7.8% | 7.1% | 6.6% |
| Age 15 to 17 | 4.7% | 4.3% | 3.9% |
| Age 18 to 20 | 4.8% | 3.8% | 4.0% |
| Age 21 to 24 | 5.2% | 5.4% | 5.2% |
| Age 25 to 34 | 15.7% | 15.8% | 13.8% |
| Age 35 to 44 | 14.0% | 13.0% | 12.9% |
| Age 45 to 54 | 10.8% | 13.6% | 12.6% |
| Age 55 to 59 | 4.6% | 5.8% | 6.7% |
| Age 60 to 64 | 5.3% | 5.7% | 6.3% |
| Age 65 to 74 | 6.7% | 8.4% | 9.6% |
| Age 75 to 84 | 2.9% | 3.2% | 4.5% |
| Age 85 and over | 1.3% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Selma, CA | Downey, CA | United States |
| White | 11.3% | 13.9% | 59.4% |
| Black | 0.8% | 3.5% | 12.2% |
| Asian | 1.4% | 6.5% | 5.6% |
| Native American | 0.1% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.2% | 0.2% |
| Other | 0.4% | 0.3% | 0.4% |
| Two or More Races | 1.3% | 1.4% | 3.2% |
| Hispanic | 84.8% | 74.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Selma, CA | Downey, CA | United States |
| Married Population | 45.0% | 46.3% | 49.8% |
| Currently Married | 41.2% | 44.2% | 48.0% |
| Married but Separated | 3.8% | 2.1% | 1.8% |
| Single Population | 55.0% | 53.7% | 50.2% |
| Never Married | 38.6% | 39.8% | 33.8% |
| Divorced | 10.6% | 9.3% | 10.8% |
| Widowed | 5.8% | 4.5% | 5.6% |
| space5 | | | |
| Household Size | 3.40 | 3.29 | 2.60 |
| Households | 7,179 | 34,497 | 124,010,992 |
| Family Households | 5,563 | 27,400 | 80,755,759 |
| Married couple, w/children | 33.3% | 31.7% | 30.5% |
| Married couple, no children | 22.7% | 32.0% | 42.9% |
| Non Family Households | 1,616 | 7,097 | 43,255,233 |
| Single householder, w/children | 25.4% | 20.3% | 15.8% |
| Single householder, no children | 18.6% | 16.0% | 10.8% |