| | Herndon, VA | Lafayette, IN | United States |
| Population | 24,574 | 70,928 | 329,725,481 |
| Female Population | 48.4% | 50.1% | 50.5% |
| Male Population | 51.6% | 49.9% | 49.5% |
| Median Age | 35.7 | 32.5 | 38.4 |
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| Population - 2010 | 23,400 | 68,926 | 309,327,143 |
| Population - 2000 | 21,655 | 56,397 | 285,036,114 |
| Population - 1990 | 16,139 | 43,764 | 251,960,433 |
| Pop. 2000 to Now | 13.5% | 26.8% | 15.6% |
| Pop. 1990 to Now | 52.3% | 63.3% | 30.8% |
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| Population Density | 5,732.2 | 2,414.3 | 93.4 |
| Land Area | 4.3 | 29.4 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Herndon, VA | Lafayette, IN | United States |
| Age 0 to 4 | 6.9% | 7.8% | 5.9% |
| Age 5 to 9 | 7.2% | 6.3% | 6.1% |
| Age 10 to 14 | 5.7% | 6.1% | 6.6% |
| Age 15 to 17 | 4.0% | 3.2% | 3.9% |
| Age 18 to 20 | 3.1% | 3.3% | 4.0% |
| Age 21 to 24 | 6.0% | 9.2% | 5.2% |
| Age 25 to 34 | 15.9% | 18.0% | 13.8% |
| Age 35 to 44 | 16.5% | 13.0% | 12.9% |
| Age 45 to 54 | 12.8% | 9.6% | 12.6% |
| Age 55 to 59 | 6.5% | 4.9% | 6.7% |
| Age 60 to 64 | 5.4% | 5.3% | 6.3% |
| Age 65 to 74 | 6.8% | 7.9% | 9.6% |
| Age 75 to 84 | 2.9% | 3.8% | 4.5% |
| Age 85 and over | 0.4% | 1.5% | 1.9% |
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| Race | | | |
| | Herndon, VA | Lafayette, IN | United States |
| White | 35.4% | 73.4% | 59.4% |
| Black | 7.0% | 8.7% | 12.2% |
| Asian | 16.1% | 1.8% | 5.6% |
| Native American | 0.7% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.8% | 0.5% | 0.4% |
| Two or More Races | 3.3% | 2.5% | 3.2% |
| Hispanic | 36.7% | 13.0% | 18.4% |
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| Marriage & Family | | | |
| | Herndon, VA | Lafayette, IN | United States |
| Married Population | 55.6% | 42.3% | 49.8% |
| Currently Married | 54.1% | 40.4% | 48.0% |
| Married but Separated | 1.5% | 1.9% | 1.8% |
| Single Population | 44.4% | 57.7% | 50.2% |
| Never Married | 34.8% | 38.0% | 33.8% |
| Divorced | 7.3% | 14.5% | 10.8% |
| Widowed | 2.3% | 5.2% | 5.6% |
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| Household Size | 3.10 | 2.22 | 2.60 |
| Households | 7,914 | 31,362 | 124,010,992 |
| Family Households | 5,747 | 16,889 | 80,755,759 |
| Married couple, w/children | 40.3% | 24.3% | 30.5% |
| Married couple, no children | 39.5% | 39.4% | 42.9% |
| Non Family Households | 2,167 | 14,473 | 43,255,233 |
| Single householder, w/children | 12.2% | 24.5% | 15.8% |
| Single householder, no children | 8.1% | 11.8% | 10.8% |