| | Westfield, NJ | Champaign, IL | United States |
| Population | 30,950 | 88,343 | 329,725,481 |
| Female Population | 51.6% | 48.4% | 50.5% |
| Male Population | 48.4% | 51.6% | 49.5% |
| Median Age | 40.9 | 26.9 | 38.4 |
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| Population - 2010 | 30,336 | 81,406 | 309,327,143 |
| Population - 2000 | 29,644 | 67,518 | 285,036,114 |
| Population - 1990 | 28,870 | 63,502 | 251,960,433 |
| Pop. 2000 to Now | -1.4% | 32.4% | 15.6% |
| Pop. 1990 to Now | 1.3% | 40.8% | 30.8% |
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| Population Density | 4,602.9 | 3,869.4 | 93.4 |
| Land Area | 6.7 | 22.8 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Westfield, NJ | Champaign, IL | United States |
| Age 0 to 4 | 6.9% | 5.1% | 5.9% |
| Age 5 to 9 | 8.3% | 5.0% | 6.1% |
| Age 10 to 14 | 9.6% | 5.0% | 6.6% |
| Age 15 to 17 | 4.3% | 2.6% | 3.9% |
| Age 18 to 20 | 3.5% | 14.1% | 4.0% |
| Age 21 to 24 | 3.5% | 14.8% | 5.2% |
| Age 25 to 34 | 7.2% | 14.8% | 13.8% |
| Age 35 to 44 | 12.2% | 10.8% | 12.9% |
| Age 45 to 54 | 16.7% | 8.7% | 12.6% |
| Age 55 to 59 | 8.3% | 4.3% | 6.7% |
| Age 60 to 64 | 5.0% | 4.1% | 6.3% |
| Age 65 to 74 | 9.1% | 6.4% | 9.6% |
| Age 75 to 84 | 3.7% | 3.3% | 4.5% |
| Age 85 and over | 1.6% | 1.0% | 1.9% |
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| Race | | | |
| | Westfield, NJ | Champaign, IL | United States |
| White | 77.6% | 57.1% | 59.4% |
| Black | 2.2% | 17.7% | 12.2% |
| Asian | 7.5% | 15.0% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.3% | 0.3% | 0.4% |
| Two or More Races | 3.3% | 3.2% | 3.2% |
| Hispanic | 9.0% | 6.6% | 18.4% |
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| Marriage & Family | | | |
| | Westfield, NJ | Champaign, IL | United States |
| Married Population | 65.1% | 34.9% | 49.8% |
| Currently Married | 64.4% | 33.9% | 48.0% |
| Married but Separated | 0.7% | 1.0% | 1.8% |
| Single Population | 34.9% | 65.1% | 50.2% |
| Never Married | 23.3% | 54.5% | 33.8% |
| Divorced | 6.7% | 7.9% | 10.8% |
| Widowed | 4.8% | 2.7% | 5.6% |
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| Household Size | 2.91 | 2.28 | 2.60 |
| Households | 10,514 | 35,206 | 124,010,992 |
| Family Households | 8,185 | 16,072 | 80,755,759 |
| Married couple, w/children | 47.0% | 31.8% | 30.5% |
| Married couple, no children | 43.6% | 40.6% | 42.9% |
| Non Family Households | 2,329 | 19,134 | 43,255,233 |
| Single householder, w/children | 6.5% | 17.8% | 15.8% |
| Single householder, no children | 3.0% | 9.9% | 10.8% |