| | Brookville, PA | Clarion, PA | United States |
| Population | 3,982 | 4,046 | 329,725,481 |
| Female Population | 48.5% | 56.1% | 50.5% |
| Male Population | 51.5% | 43.9% | 49.5% |
| Median Age | 37.7 | 23.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,928 | 5,263 | 309,327,143 |
| Population - 2000 | 4,230 | 6,185 | 285,036,114 |
| Population - 1990 | 4,184 | 6,457 | 251,960,433 |
| Pop. 2000 to Now | -11.1% | -8.0% | 15.6% |
| Pop. 1990 to Now | -10.1% | -11.8% | 30.8% |
| space4 | | | |
| Population Density | 1,269.4 | 2,570.5 | 93.4 |
| Land Area | 3.1 | 1.6 | 3,531,905.4 |
| Water Area | 0.1 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Brookville, PA | Clarion, PA | United States |
| Age 0 to 4 | 5.5% | 5.5% | 5.9% |
| Age 5 to 9 | 10.2% | 4.8% | 6.1% |
| Age 10 to 14 | 4.2% | 6.3% | 6.6% |
| Age 15 to 17 | 2.3% | 2.0% | 3.9% |
| Age 18 to 20 | 1.9% | 17.0% | 4.0% |
| Age 21 to 24 | 6.6% | 16.6% | 5.2% |
| Age 25 to 34 | 15.3% | 15.7% | 13.8% |
| Age 35 to 44 | 13.2% | 7.6% | 12.9% |
| Age 45 to 54 | 9.2% | 7.6% | 12.6% |
| Age 55 to 59 | 8.9% | 1.8% | 6.7% |
| Age 60 to 64 | 3.9% | 3.4% | 6.3% |
| Age 65 to 74 | 9.3% | 6.6% | 9.6% |
| Age 75 to 84 | 6.6% | 3.6% | 4.5% |
| Age 85 and over | 3.0% | 1.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Brookville, PA | Clarion, PA | United States |
| White | 93.4% | 88.7% | 59.4% |
| Black | 0.4% | 5.4% | 12.2% |
| Asian | 0.0% | 1.6% | 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 | 2.4% | 0.3% | 3.2% |
| Hispanic | 3.8% | 4.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Brookville, PA | Clarion, PA | United States |
| Married Population | 54.5% | 27.2% | 49.8% |
| Currently Married | 52.3% | 26.3% | 48.0% |
| Married but Separated | 2.3% | 0.9% | 1.8% |
| Single Population | 45.5% | 72.8% | 50.2% |
| Never Married | 27.5% | 59.3% | 33.8% |
| Divorced | 11.0% | 7.2% | 10.8% |
| Widowed | 7.0% | 6.3% | 5.6% |
| space5 | | | |
| Household Size | 2.37 | 2.49 | 2.60 |
| Households | 1,645 | 1,375 | 124,010,992 |
| Family Households | 987 | 653 | 80,755,759 |
| Married couple, w/children | 32.1% | 40.1% | 30.5% |
| Married couple, no children | 44.0% | 28.2% | 42.9% |
| Non Family Households | 658 | 722 | 43,255,233 |
| Single householder, w/children | 16.1% | 21.7% | 15.8% |
| Single householder, no children | 7.8% | 10.0% | 10.8% |