| | Cumby, TX | Dallas, TX | United States |
| Population | 807 | 1,300,239 | 329,725,481 |
| Female Population | 56.6% | 50.2% | 50.5% |
| Male Population | 43.4% | 49.8% | 49.5% |
| Median Age | 38.3 | 33.1 | 38.4 |
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| Population - 2010 | 776 | 1,200,360 | 309,327,143 |
| Population - 2000 | 616 | 1,188,580 | 285,036,114 |
| Population - 1990 | 571 | 1,006,877 | 251,960,433 |
| Pop. 2000 to Now | 28.9% | 13.0% | 15.6% |
| Pop. 1990 to Now | 39.1% | 33.4% | 30.8% |
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| Population Density | 796.6 | 3,828.5 | 93.4 |
| Land Area | 1.0 | 339.6 | 3,531,905.4 |
| Water Area | 0.0 | 44.8 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Cumby, TX | Dallas, TX | United States |
| Age 0 to 4 | 5.6% | 7.2% | 5.9% |
| Age 5 to 9 | 5.3% | 6.8% | 6.1% |
| Age 10 to 14 | 8.1% | 6.9% | 6.6% |
| Age 15 to 17 | 6.9% | 3.9% | 3.9% |
| Age 18 to 20 | 3.1% | 3.5% | 4.0% |
| Age 21 to 24 | 2.5% | 6.2% | 5.2% |
| Age 25 to 34 | 13.4% | 18.7% | 13.8% |
| Age 35 to 44 | 13.6% | 13.9% | 12.9% |
| Age 45 to 54 | 11.3% | 11.7% | 12.6% |
| Age 55 to 59 | 5.6% | 5.6% | 6.7% |
| Age 60 to 64 | 6.7% | 5.1% | 6.3% |
| Age 65 to 74 | 8.9% | 6.6% | 9.6% |
| Age 75 to 84 | 8.3% | 2.9% | 4.5% |
| Age 85 and over | 0.7% | 1.3% | 1.9% |
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| Race | | | |
| | Cumby, TX | Dallas, TX | United States |
| White | 91.8% | 28.6% | 59.4% |
| Black | 1.9% | 23.7% | 12.2% |
| Asian | 0.0% | 3.5% | 5.6% |
| Native American | 0.7% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.6% | 0.0% | 0.2% |
| Other | 1.2% | 0.2% | 0.4% |
| Two or More Races | 0.6% | 1.9% | 3.2% |
| Hispanic | 3.1% | 42.0% | 18.4% |
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| Marriage & Family | | | |
| | Cumby, TX | Dallas, TX | United States |
| Married Population | 61.8% | 43.1% | 49.8% |
| Currently Married | 59.0% | 40.2% | 48.0% |
| Married but Separated | 2.8% | 2.9% | 1.8% |
| Single Population | 38.2% | 56.9% | 50.2% |
| Never Married | 20.8% | 42.3% | 33.8% |
| Divorced | 11.5% | 10.3% | 10.8% |
| Widowed | 6.0% | 4.3% | 5.6% |
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| Household Size | 2.65 | 2.49 | 2.60 |
| Households | 305 | 515,138 | 124,010,992 |
| Family Households | 219 | 285,599 | 80,755,759 |
| Married couple, w/children | 38.8% | 30.0% | 30.5% |
| Married couple, no children | 47.9% | 34.0% | 42.9% |
| Non Family Households | 86 | 229,539 | 43,255,233 |
| Single householder, w/children | 12.8% | 22.3% | 15.8% |
| Single householder, no children | 0.5% | 13.7% | 10.8% |