| | Reston, VA | Cary, NC | United States |
| Population | 62,453 | 171,603 | 329,725,481 |
| Female Population | 51.9% | 50.6% | 50.5% |
| Male Population | 48.1% | 49.4% | 49.5% |
| Median Age | 39.6 | 39.1 | 38.4 |
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| Population - 2010 | 53,257 | 137,116 | 309,327,143 |
| Population - 2000 | 56,407 | 94,536 | 285,036,114 |
| Population - 1990 | 48,556 | 43,858 | 251,960,433 |
| Pop. 2000 to Now | 7.9% | 83.6% | 15.6% |
| Pop. 1990 to Now | 25.4% | 295.8% | 30.8% |
| space4 | | | |
| Population Density | 4,074.7 | 2,995.2 | 93.4 |
| Land Area | 15.3 | 57.3 | 3,531,905.4 |
| Water Area | 0.3 | 1.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Reston, VA | Cary, NC | United States |
| Age 0 to 4 | 5.6% | 5.5% | 5.9% |
| Age 5 to 9 | 6.3% | 7.3% | 6.1% |
| Age 10 to 14 | 4.9% | 7.9% | 6.6% |
| Age 15 to 17 | 2.7% | 4.7% | 3.9% |
| Age 18 to 20 | 2.4% | 2.8% | 4.0% |
| Age 21 to 24 | 4.7% | 4.0% | 5.2% |
| Age 25 to 34 | 16.3% | 11.6% | 13.8% |
| Age 35 to 44 | 14.2% | 15.6% | 12.9% |
| Age 45 to 54 | 13.1% | 15.7% | 12.6% |
| Age 55 to 59 | 7.1% | 6.5% | 6.7% |
| Age 60 to 64 | 6.9% | 5.8% | 6.3% |
| Age 65 to 74 | 9.4% | 7.7% | 9.6% |
| Age 75 to 84 | 5.2% | 3.6% | 4.5% |
| Age 85 and over | 1.1% | 1.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Reston, VA | Cary, NC | United States |
| White | 59.9% | 59.6% | 59.4% |
| Black | 8.9% | 7.7% | 12.2% |
| Asian | 11.7% | 20.2% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.7% | 0.6% | 0.4% |
| Two or More Races | 5.3% | 3.4% | 3.2% |
| Hispanic | 13.6% | 8.3% | 18.4% |
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| Marriage & Family | | | |
| | Reston, VA | Cary, NC | United States |
| Married Population | 53.1% | 62.5% | 49.8% |
| Currently Married | 51.5% | 60.7% | 48.0% |
| Married but Separated | 1.6% | 1.8% | 1.8% |
| Single Population | 46.9% | 37.5% | 50.2% |
| Never Married | 32.3% | 25.7% | 33.8% |
| Divorced | 11.2% | 8.0% | 10.8% |
| Widowed | 3.5% | 3.8% | 5.6% |
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| Household Size | 2.28 | 2.66 | 2.60 |
| Households | 27,366 | 64,512 | 124,010,992 |
| Family Households | 16,101 | 46,511 | 80,755,759 |
| Married couple, w/children | 31.0% | 42.4% | 30.5% |
| Married couple, no children | 47.4% | 41.9% | 42.9% |
| Non Family Households | 11,265 | 18,001 | 43,255,233 |
| Single householder, w/children | 12.0% | 10.4% | 15.8% |
| Single householder, no children | 9.5% | 5.3% | 10.8% |