| | Niles, IL | Brookfield, IL | United States |
| Population | 30,971 | 19,517 | 329,725,481 |
| Female Population | 51.3% | 53.8% | 50.5% |
| Male Population | 48.7% | 46.2% | 49.5% |
| Median Age | 46.8 | 40.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 29,868 | 18,982 | 309,327,143 |
| Population - 2000 | 30,068 | 19,085 | 285,036,114 |
| Population - 1990 | 28,284 | 18,876 | 251,960,433 |
| Pop. 2000 to Now | -4.8% | -5.2% | 15.6% |
| Pop. 1990 to Now | 1.2% | -4.2% | 30.8% |
| space4 | | | |
| Population Density | 5,297.8 | 6,371.9 | 93.4 |
| Land Area | 5.8 | 3.1 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Niles, IL | Brookfield, IL | United States |
| Age 0 to 4 | 4.7% | 6.6% | 5.9% |
| Age 5 to 9 | 5.8% | 7.9% | 6.1% |
| Age 10 to 14 | 4.2% | 6.5% | 6.6% |
| Age 15 to 17 | 3.4% | 4.3% | 3.9% |
| Age 18 to 20 | 2.4% | 2.5% | 4.0% |
| Age 21 to 24 | 4.1% | 2.6% | 5.2% |
| Age 25 to 34 | 11.1% | 9.1% | 13.8% |
| Age 35 to 44 | 12.2% | 17.4% | 12.9% |
| Age 45 to 54 | 12.6% | 15.5% | 12.6% |
| Age 55 to 59 | 7.5% | 7.4% | 6.7% |
| Age 60 to 64 | 6.6% | 7.4% | 6.3% |
| Age 65 to 74 | 10.5% | 7.6% | 9.6% |
| Age 75 to 84 | 7.7% | 3.6% | 4.5% |
| Age 85 and over | 7.3% | 1.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Niles, IL | Brookfield, IL | United States |
| White | 65.2% | 71.5% | 59.4% |
| Black | 2.2% | 3.7% | 12.2% |
| Asian | 17.9% | 1.2% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.2% | 0.4% |
| Two or More Races | 2.0% | 2.9% | 3.2% |
| Hispanic | 12.5% | 20.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Niles, IL | Brookfield, IL | United States |
| Married Population | 53.3% | 54.7% | 49.8% |
| Currently Married | 52.1% | 53.4% | 48.0% |
| Married but Separated | 1.2% | 1.3% | 1.8% |
| Single Population | 46.7% | 45.3% | 50.2% |
| Never Married | 28.4% | 29.6% | 33.8% |
| Divorced | 7.6% | 10.6% | 10.8% |
| Widowed | 10.7% | 5.0% | 5.6% |
| space5 | | | |
| Household Size | 2.55 | 2.55 | 2.60 |
| Households | 11,669 | 7,590 | 124,010,992 |
| Family Households | 7,740 | 5,005 | 80,755,759 |
| Married couple, w/children | 36.3% | 39.2% | 30.5% |
| Married couple, no children | 42.1% | 41.4% | 42.9% |
| Non Family Households | 3,929 | 2,585 | 43,255,233 |
| Single householder, w/children | 6.8% | 11.1% | 15.8% |
| Single householder, no children | 14.7% | 8.3% | 10.8% |