| | Welby, CO | Detroit, MI | United States |
| Population | 16,260 | 645,658 | 329,725,481 |
| Female Population | 47.7% | 52.5% | 50.5% |
| Male Population | 52.3% | 47.5% | 49.5% |
| Median Age | 33.7 | 35 | 38.4 |
| space3 | | | |
| Population - 2010 | 13,964 | 711,198 | 309,327,143 |
| Population - 2000 | 12,973 | 951,270 | 285,036,114 |
| Population - 1990 | 10,218 | 1,027,974 | 251,960,433 |
| Pop. 2000 to Now | 30.8% | -30.1% | 15.6% |
| Pop. 1990 to Now | 66.0% | -35.3% | 30.8% |
| space4 | | | |
| Population Density | 4,392.2 | 4,654.6 | 93.4 |
| Land Area | 3.7 | 138.7 | 3,531,905.4 |
| Water Area | 0.1 | 4.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Welby, CO | Detroit, MI | United States |
| Age 0 to 4 | 5.6% | 7.1% | 5.9% |
| Age 5 to 9 | 6.3% | 6.7% | 6.1% |
| Age 10 to 14 | 5.9% | 7.1% | 6.6% |
| Age 15 to 17 | 4.7% | 4.0% | 3.9% |
| Age 18 to 20 | 3.8% | 4.2% | 4.0% |
| Age 21 to 24 | 7.7% | 5.5% | 5.2% |
| Age 25 to 34 | 19.7% | 15.4% | 13.8% |
| Age 35 to 44 | 14.8% | 11.7% | 12.9% |
| Age 45 to 54 | 12.8% | 11.9% | 12.6% |
| Age 55 to 59 | 6.9% | 6.1% | 6.7% |
| Age 60 to 64 | 3.7% | 6.2% | 6.3% |
| Age 65 to 74 | 5.9% | 8.5% | 9.6% |
| Age 75 to 84 | 1.8% | 3.9% | 4.5% |
| Age 85 and over | 0.4% | 1.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Welby, CO | Detroit, MI | United States |
| White | 34.4% | 10.1% | 59.4% |
| Black | 1.5% | 77.5% | 12.2% |
| Asian | 2.4% | 1.6% | 5.6% |
| Native American | 0.1% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.5% | 0.4% |
| Two or More Races | 2.0% | 2.2% | 3.2% |
| Hispanic | 59.6% | 7.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Welby, CO | Detroit, MI | United States |
| Married Population | 45.3% | 25.1% | 49.8% |
| Currently Married | 42.7% | 22.1% | 48.0% |
| Married but Separated | 2.6% | 3.0% | 1.8% |
| Single Population | 54.7% | 74.9% | 50.2% |
| Never Married | 38.1% | 56.0% | 33.8% |
| Divorced | 12.1% | 12.4% | 10.8% |
| Widowed | 4.4% | 6.5% | 5.6% |
| space5 | | | |
| Household Size | 2.86 | 2.53 | 2.60 |
| Households | 5,685 | 250,096 | 124,010,992 |
| Family Households | 3,849 | 129,711 | 80,755,759 |
| Married couple, w/children | 34.4% | 15.7% | 30.5% |
| Married couple, no children | 32.0% | 21.4% | 42.9% |
| Non Family Households | 1,836 | 120,385 | 43,255,233 |
| Single householder, w/children | 16.6% | 37.5% | 15.8% |
| Single householder, no children | 17.0% | 25.3% | 10.8% |