| | Buffalo Grove, IL | Appleton, WI | United States |
| Population | 43,062 | 74,752 | 329,725,481 |
| Female Population | 52.4% | 50.5% | 50.5% |
| Male Population | 47.6% | 49.5% | 49.5% |
| Median Age | 41.2 | 36.5 | 38.4 |
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| Population - 2010 | 41,543 | 72,616 | 309,327,143 |
| Population - 2000 | 42,909 | 70,087 | 285,036,114 |
| Population - 1990 | 36,427 | 65,695 | 251,960,433 |
| Pop. 2000 to Now | -6.4% | 5.7% | 15.6% |
| Pop. 1990 to Now | 10.3% | 12.7% | 30.8% |
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| Population Density | 4,540.0 | 3,056.5 | 93.4 |
| Land Area | 9.5 | 24.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.5 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Buffalo Grove, IL | Appleton, WI | United States |
| Age 0 to 4 | 6.0% | 6.4% | 5.9% |
| Age 5 to 9 | 5.8% | 6.7% | 6.1% |
| Age 10 to 14 | 7.1% | 6.4% | 6.6% |
| Age 15 to 17 | 5.4% | 4.5% | 3.9% |
| Age 18 to 20 | 2.9% | 4.3% | 4.0% |
| Age 21 to 24 | 4.0% | 5.4% | 5.2% |
| Age 25 to 34 | 10.0% | 14.2% | 13.8% |
| Age 35 to 44 | 14.9% | 13.3% | 12.9% |
| Age 45 to 54 | 15.5% | 12.4% | 12.6% |
| Age 55 to 59 | 7.3% | 6.8% | 6.7% |
| Age 60 to 64 | 7.1% | 5.4% | 6.3% |
| Age 65 to 74 | 9.3% | 8.4% | 9.6% |
| Age 75 to 84 | 2.9% | 3.9% | 4.5% |
| Age 85 and over | 1.8% | 1.9% | 1.9% |
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| Race | | | |
| | Buffalo Grove, IL | Appleton, WI | United States |
| White | 63.2% | 79.9% | 59.4% |
| Black | 3.2% | 3.0% | 12.2% |
| Asian | 24.0% | 7.2% | 5.6% |
| Native American | 0.2% | 0.4% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.2% | 0.0% | 0.4% |
| Two or More Races | 2.6% | 3.0% | 3.2% |
| Hispanic | 6.5% | 6.4% | 18.4% |
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| Marriage & Family | | | |
| | Buffalo Grove, IL | Appleton, WI | United States |
| Married Population | 63.1% | 49.5% | 49.8% |
| Currently Married | 62.3% | 48.7% | 48.0% |
| Married but Separated | 0.7% | 0.8% | 1.8% |
| Single Population | 36.9% | 50.5% | 50.2% |
| Never Married | 25.1% | 34.9% | 33.8% |
| Divorced | 7.9% | 11.3% | 10.8% |
| Widowed | 3.9% | 4.4% | 5.6% |
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| Household Size | 2.69 | 2.41 | 2.60 |
| Households | 15,982 | 29,926 | 124,010,992 |
| Family Households | 11,906 | 18,716 | 80,755,759 |
| Married couple, w/children | 42.1% | 32.6% | 30.5% |
| Married couple, no children | 44.1% | 43.9% | 42.9% |
| Non Family Households | 4,076 | 11,210 | 43,255,233 |
| Single householder, w/children | 8.1% | 16.7% | 15.8% |
| Single householder, no children | 5.6% | 6.8% | 10.8% |