| | Kildeer, IL | Foster City, CA | United States |
| Population | 4,093 | 33,511 | 329,725,481 |
| Female Population | 49.5% | 50.8% | 50.5% |
| Male Population | 50.5% | 49.3% | 49.5% |
| Median Age | 43.6 | 39.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,905 | 30,597 | 309,327,143 |
| Population - 2000 | 3,460 | 28,803 | 285,036,114 |
| Population - 1990 | 2,257 | 28,176 | 251,960,433 |
| Pop. 2000 to Now | 15.4% | 14.2% | 15.6% |
| Pop. 1990 to Now | 76.9% | 16.7% | 30.8% |
| space4 | | | |
| Population Density | 967.6 | 8,828.0 | 93.4 |
| Land Area | 4.2 | 3.8 | 3,531,905.4 |
| Water Area | 0.2 | 16.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Kildeer, IL | Foster City, CA | United States |
| Age 0 to 4 | 6.4% | 5.6% | 5.9% |
| Age 5 to 9 | 6.3% | 7.2% | 6.1% |
| Age 10 to 14 | 8.0% | 5.9% | 6.6% |
| Age 15 to 17 | 7.3% | 3.9% | 3.9% |
| Age 18 to 20 | 3.3% | 1.8% | 4.0% |
| Age 21 to 24 | 4.0% | 2.7% | 5.2% |
| Age 25 to 34 | 3.7% | 15.4% | 13.8% |
| Age 35 to 44 | 12.9% | 16.9% | 12.9% |
| Age 45 to 54 | 20.2% | 12.7% | 12.6% |
| Age 55 to 59 | 9.8% | 5.8% | 6.7% |
| Age 60 to 64 | 5.9% | 5.2% | 6.3% |
| Age 65 to 74 | 8.4% | 8.5% | 9.6% |
| Age 75 to 84 | 3.2% | 6.0% | 4.5% |
| Age 85 and over | 0.5% | 2.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Kildeer, IL | Foster City, CA | United States |
| White | 72.6% | 31.0% | 59.4% |
| Black | 0.0% | 2.4% | 12.2% |
| Asian | 20.0% | 51.8% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.2% | 0.2% |
| Other | 0.0% | 0.1% | 0.4% |
| Two or More Races | 2.4% | 5.6% | 3.2% |
| Hispanic | 5.1% | 8.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Kildeer, IL | Foster City, CA | United States |
| Married Population | 75.5% | 62.4% | 49.8% |
| Currently Married | 74.7% | 61.1% | 48.0% |
| Married but Separated | 0.8% | 1.2% | 1.8% |
| Single Population | 24.5% | 37.6% | 50.2% |
| Never Married | 21.6% | 25.6% | 33.8% |
| Divorced | 1.9% | 6.2% | 10.8% |
| Widowed | 1.0% | 5.8% | 5.6% |
| space5 | | | |
| Household Size | 3.11 | 2.67 | 2.60 |
| Households | 1,317 | 12,475 | 124,010,992 |
| Family Households | 1,212 | 8,857 | 80,755,759 |
| Married couple, w/children | 52.0% | 44.2% | 30.5% |
| Married couple, no children | 44.6% | 40.5% | 42.9% |
| Non Family Households | 105 | 3,618 | 43,255,233 |
| Single householder, w/children | 2.1% | 7.8% | 15.8% |
| Single householder, no children | 1.4% | 7.6% | 10.8% |