| | Welch, TX | Sundown, TX | United States |
| Population | 210 | 1,424 | 329,725,481 |
| Female Population | 53.3% | 46.9% | 50.5% |
| Male Population | 46.7% | 53.1% | 49.5% |
| Median Age | 25.8 | 33.7 | 38.4 |
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| Population - 2010 | 119 | 1,388 | 309,327,143 |
| Population - 2000 | 159 | 1,505 | 285,036,114 |
| Population - 1990 | 176 | 1,759 | 251,960,433 |
| Pop. 2000 to Now | 33.3% | -6.1% | 15.6% |
| Pop. 1990 to Now | 20.5% | -19.6% | 30.8% |
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| Population Density | 143.8 | 936.8 | 93.4 |
| Land Area | 1.5 | 1.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Welch, TX | Sundown, TX | United States |
| Age 0 to 4 | 21.4% | 6.3% | 5.9% |
| Age 5 to 9 | 6.2% | 6.5% | 6.1% |
| Age 10 to 14 | 2.9% | 9.3% | 6.6% |
| Age 15 to 17 | 8.6% | 4.6% | 3.9% |
| Age 18 to 20 | 5.2% | 4.2% | 4.0% |
| Age 21 to 24 | 3.8% | 7.2% | 5.2% |
| Age 25 to 34 | 6.2% | 13.7% | 13.8% |
| Age 35 to 44 | 7.1% | 11.0% | 12.9% |
| Age 45 to 54 | 9.0% | 14.0% | 12.6% |
| Age 55 to 59 | 5.7% | 9.1% | 6.7% |
| Age 60 to 64 | 8.6% | 3.6% | 6.3% |
| Age 65 to 74 | 9.0% | 7.3% | 9.6% |
| Age 75 to 84 | 6.2% | 2.2% | 4.5% |
| Age 85 and over | 0.0% | 1.1% | 1.9% |
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| Race | | | |
| | Welch, TX | Sundown, TX | United States |
| White | 57.1% | 48.7% | 59.4% |
| Black | 0.0% | 0.6% | 12.2% |
| Asian | 0.0% | 0.6% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 1.9% | 2.0% | 3.2% |
| Hispanic | 41.0% | 48.0% | 18.4% |
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| Marriage & Family | | | |
| | Welch, TX | Sundown, TX | United States |
| Married Population | 67.1% | 56.7% | 49.8% |
| Currently Married | 65.8% | 52.3% | 48.0% |
| Married but Separated | 1.4% | 4.4% | 1.8% |
| Single Population | 32.9% | 43.3% | 50.2% |
| Never Married | 30.1% | 26.7% | 33.8% |
| Divorced | 1.4% | 10.4% | 10.8% |
| Widowed | 1.4% | 6.3% | 5.6% |
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| Household Size | 3.44 | 2.83 | 2.60 |
| Households | 61 | 499 | 124,010,992 |
| Family Households | 47 | 383 | 80,755,759 |
| Married couple, w/children | 57.4% | 33.2% | 30.5% |
| Married couple, no children | 42.6% | 42.8% | 42.9% |
| Non Family Households | 14 | 116 | 43,255,233 |
| Single householder, w/children | 0.0% | 16.2% | 15.8% |
| Single householder, no children | 0.0% | 7.8% | 10.8% |