| | Willoughby Hills, OH | Clarksville, IN | United States |
| Population | 9,929 | 22,169 | 329,725,481 |
| Female Population | 52.2% | 51.9% | 50.5% |
| Male Population | 47.8% | 48.1% | 49.5% |
| Median Age | 37.5 | 40.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 9,490 | 21,580 | 309,327,143 |
| Population - 2000 | 8,595 | 21,400 | 285,036,114 |
| Population - 1990 | 8,427 | 19,833 | 251,960,433 |
| Pop. 2000 to Now | 11.0% | 0.2% | 15.6% |
| Pop. 1990 to Now | 13.2% | 8.1% | 30.8% |
| space4 | | | |
| Population Density | 922.7 | 2,225.1 | 93.4 |
| Land Area | 10.8 | 10.0 | 3,531,905.4 |
| Water Area | 0.1 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Willoughby Hills, OH | Clarksville, IN | United States |
| Age 0 to 4 | 4.8% | 6.2% | 5.9% |
| Age 5 to 9 | 4.1% | 4.7% | 6.1% |
| Age 10 to 14 | 5.6% | 5.4% | 6.6% |
| Age 15 to 17 | 3.4% | 3.6% | 3.9% |
| Age 18 to 20 | 2.4% | 3.3% | 4.0% |
| Age 21 to 24 | 5.7% | 5.6% | 5.2% |
| Age 25 to 34 | 17.1% | 15.0% | 13.8% |
| Age 35 to 44 | 14.4% | 13.6% | 12.9% |
| Age 45 to 54 | 10.0% | 12.9% | 12.6% |
| Age 55 to 59 | 7.5% | 6.1% | 6.7% |
| Age 60 to 64 | 7.2% | 5.9% | 6.3% |
| Age 65 to 74 | 9.0% | 10.4% | 9.6% |
| Age 75 to 84 | 7.1% | 4.6% | 4.5% |
| Age 85 and over | 1.6% | 2.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Willoughby Hills, OH | Clarksville, IN | United States |
| White | 74.3% | 78.2% | 59.4% |
| Black | 16.8% | 6.4% | 12.2% |
| Asian | 6.3% | 1.1% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.4% | 2.4% | 3.2% |
| Hispanic | 2.2% | 11.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Willoughby Hills, OH | Clarksville, IN | United States |
| Married Population | 49.6% | 40.8% | 49.8% |
| Currently Married | 48.5% | 37.8% | 48.0% |
| Married but Separated | 1.1% | 3.0% | 1.8% |
| Single Population | 50.4% | 59.2% | 50.2% |
| Never Married | 35.5% | 36.0% | 33.8% |
| Divorced | 11.1% | 16.6% | 10.8% |
| Widowed | 3.7% | 6.7% | 5.6% |
| space5 | | | |
| Household Size | 2.04 | 2.44 | 2.60 |
| Households | 4,861 | 8,951 | 124,010,992 |
| Family Households | 2,744 | 4,693 | 80,755,759 |
| Married couple, w/children | 24.4% | 28.4% | 30.5% |
| Married couple, no children | 47.5% | 37.2% | 42.9% |
| Non Family Households | 2,117 | 4,258 | 43,255,233 |
| Single householder, w/children | 15.8% | 17.0% | 15.8% |
| Single householder, no children | 12.3% | 17.4% | 10.8% |