| | Niles, IL | Park Ridge, IL | United States |
| Population | 30,971 | 39,562 | 329,725,481 |
| Female Population | 51.3% | 51.2% | 50.5% |
| Male Population | 48.7% | 48.8% | 49.5% |
| Median Age | 46.8 | 45 | 38.4 |
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| Population - 2010 | 29,868 | 37,498 | 309,327,143 |
| Population - 2000 | 30,068 | 37,775 | 285,036,114 |
| Population - 1990 | 28,284 | 36,175 | 251,960,433 |
| Pop. 2000 to Now | -4.8% | -3.3% | 15.6% |
| Pop. 1990 to Now | 1.2% | 0.9% | 30.8% |
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| Population Density | 5,297.8 | 5,581.6 | 93.4 |
| Land Area | 5.8 | 7.1 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Niles, IL | Park Ridge, IL | United States |
| Age 0 to 4 | 4.7% | 5.5% | 5.9% |
| Age 5 to 9 | 5.8% | 8.1% | 6.1% |
| Age 10 to 14 | 4.2% | 6.1% | 6.6% |
| Age 15 to 17 | 3.4% | 3.8% | 3.9% |
| Age 18 to 20 | 2.4% | 2.9% | 4.0% |
| Age 21 to 24 | 4.1% | 3.1% | 5.2% |
| Age 25 to 34 | 11.1% | 6.7% | 13.8% |
| Age 35 to 44 | 12.2% | 13.8% | 12.9% |
| Age 45 to 54 | 12.6% | 13.8% | 12.6% |
| Age 55 to 59 | 7.5% | 7.9% | 6.7% |
| Age 60 to 64 | 6.6% | 8.1% | 6.3% |
| Age 65 to 74 | 10.5% | 10.7% | 9.6% |
| Age 75 to 84 | 7.7% | 5.6% | 4.5% |
| Age 85 and over | 7.3% | 3.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | Niles, IL | Park Ridge, IL | United States |
| White | 65.2% | 85.1% | 59.4% |
| Black | 2.2% | 1.0% | 12.2% |
| Asian | 17.9% | 6.1% | 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% | 2.2% | 3.2% |
| Hispanic | 12.5% | 5.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Niles, IL | Park Ridge, IL | United States |
| Married Population | 53.3% | 60.4% | 49.8% |
| Currently Married | 52.1% | 59.0% | 48.0% |
| Married but Separated | 1.2% | 1.4% | 1.8% |
| Single Population | 46.7% | 39.6% | 50.2% |
| Never Married | 28.4% | 25.4% | 33.8% |
| Divorced | 7.6% | 7.7% | 10.8% |
| Widowed | 10.7% | 6.5% | 5.6% |
| space5 | | | |
| Household Size | 2.55 | 2.57 | 2.60 |
| Households | 11,669 | 15,199 | 124,010,992 |
| Family Households | 7,740 | 10,975 | 80,755,759 |
| Married couple, w/children | 36.3% | 36.2% | 30.5% |
| Married couple, no children | 42.1% | 45.7% | 42.9% |
| Non Family Households | 3,929 | 4,224 | 43,255,233 |
| Single householder, w/children | 6.8% | 8.2% | 15.8% |
| Single householder, no children | 14.7% | 9.9% | 10.8% |