| | Sycamore, IL | Janesville, WI | United States |
| Population | 18,144 | 65,506 | 329,725,481 |
| Female Population | 54.5% | 51.1% | 50.5% |
| Male Population | 45.5% | 48.9% | 49.5% |
| Median Age | 37.2 | 39.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 17,523 | 63,632 | 309,327,143 |
| Population - 2000 | 12,020 | 59,498 | 285,036,114 |
| Population - 1990 | 9,708 | 52,133 | 251,960,433 |
| Pop. 2000 to Now | 52.4% | 8.7% | 15.6% |
| Pop. 1990 to Now | 88.7% | 24.0% | 30.8% |
| space4 | | | |
| Population Density | 1,843.2 | 1,924.1 | 93.4 |
| Land Area | 9.8 | 34.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.6 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Sycamore, IL | Janesville, WI | United States |
| Age 0 to 4 | 5.7% | 5.1% | 5.9% |
| Age 5 to 9 | 6.4% | 6.7% | 6.1% |
| Age 10 to 14 | 7.9% | 6.9% | 6.6% |
| Age 15 to 17 | 5.1% | 4.1% | 3.9% |
| Age 18 to 20 | 4.6% | 2.9% | 4.0% |
| Age 21 to 24 | 5.2% | 5.0% | 5.2% |
| Age 25 to 34 | 12.3% | 12.7% | 13.8% |
| Age 35 to 44 | 13.8% | 13.7% | 12.9% |
| Age 45 to 54 | 12.9% | 12.6% | 12.6% |
| Age 55 to 59 | 6.0% | 6.8% | 6.7% |
| Age 60 to 64 | 7.0% | 6.9% | 6.3% |
| Age 65 to 74 | 7.5% | 9.2% | 9.6% |
| Age 75 to 84 | 4.7% | 5.0% | 4.5% |
| Age 85 and over | 1.1% | 2.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Sycamore, IL | Janesville, WI | United States |
| White | 86.5% | 86.8% | 59.4% |
| Black | 3.5% | 3.0% | 12.2% |
| Asian | 1.3% | 1.7% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 0.8% | 2.5% | 3.2% |
| Hispanic | 7.8% | 5.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Sycamore, IL | Janesville, WI | United States |
| Married Population | 52.6% | 48.7% | 49.8% |
| Currently Married | 51.0% | 47.5% | 48.0% |
| Married but Separated | 1.7% | 1.2% | 1.8% |
| Single Population | 47.4% | 51.3% | 50.2% |
| Never Married | 32.3% | 30.6% | 33.8% |
| Divorced | 11.0% | 14.4% | 10.8% |
| Widowed | 4.1% | 6.3% | 5.6% |
| space5 | | | |
| Household Size | 2.45 | 2.33 | 2.60 |
| Households | 7,328 | 27,743 | 124,010,992 |
| Family Households | 4,901 | 16,806 | 80,755,759 |
| Married couple, w/children | 29.4% | 26.5% | 30.5% |
| Married couple, no children | 44.9% | 45.2% | 42.9% |
| Non Family Households | 2,427 | 10,937 | 43,255,233 |
| Single householder, w/children | 18.7% | 18.2% | 15.8% |
| Single householder, no children | 7.0% | 10.2% | 10.8% |