| | Portia, AR | Black Rock, AR | United States |
| Population | 508 | 860 | 329,725,481 |
| Female Population | 53.4% | 45.1% | 50.5% |
| Male Population | 46.7% | 54.9% | 49.5% |
| Median Age | 45 | 36 | 38.4 |
| space3 | | | |
| Population - 2010 | 438 | 657 | 309,327,143 |
| Population - 2000 | 483 | 717 | 285,036,114 |
| Population - 1990 | 521 | 736 | 251,960,433 |
| Pop. 2000 to Now | -17.4% | -17.7% | 15.6% |
| Pop. 1990 to Now | -23.4% | -19.8% | 30.8% |
| space4 | | | |
| Population Density | 393.2 | 261.7 | 93.4 |
| Land Area | 1.3 | 3.3 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Portia, AR | Black Rock, AR | United States |
| Age 0 to 4 | 3.5% | 5.7% | 5.9% |
| Age 5 to 9 | 3.0% | 4.8% | 6.1% |
| Age 10 to 14 | 4.1% | 10.7% | 6.6% |
| Age 15 to 17 | 4.1% | 4.9% | 3.9% |
| Age 18 to 20 | 6.5% | 3.1% | 4.0% |
| Age 21 to 24 | 5.7% | 5.5% | 5.2% |
| Age 25 to 34 | 6.7% | 14.1% | 13.8% |
| Age 35 to 44 | 16.5% | 13.1% | 12.9% |
| Age 45 to 54 | 16.5% | 17.9% | 12.6% |
| Age 55 to 59 | 3.5% | 3.1% | 6.7% |
| Age 60 to 64 | 10.2% | 5.0% | 6.3% |
| Age 65 to 74 | 10.2% | 7.8% | 9.6% |
| Age 75 to 84 | 5.9% | 3.4% | 4.5% |
| Age 85 and over | 3.3% | 0.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | Portia, AR | Black Rock, AR | United States |
| White | 98.2% | 97.3% | 59.4% |
| Black | 0.2% | 0.0% | 12.2% |
| Asian | 0.0% | 0.0% | 5.6% |
| Native American | 1.0% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.6% | 2.3% | 3.2% |
| Hispanic | 0.0% | 0.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Portia, AR | Black Rock, AR | United States |
| Married Population | 38.1% | 61.5% | 49.8% |
| Currently Married | 37.7% | 61.5% | 48.0% |
| Married but Separated | 0.4% | 0.0% | 1.8% |
| Single Population | 61.9% | 38.5% | 50.2% |
| Never Married | 37.2% | 24.5% | 33.8% |
| Divorced | 15.2% | 9.1% | 10.8% |
| Widowed | 9.5% | 4.9% | 5.6% |
| space5 | | | |
| Household Size | 2.37 | 2.88 | 2.60 |
| Households | 210 | 299 | 124,010,992 |
| Family Households | 129 | 244 | 80,755,759 |
| Married couple, w/children | 17.8% | 35.2% | 30.5% |
| Married couple, no children | 41.1% | 39.8% | 42.9% |
| Non Family Households | 81 | 55 | 43,255,233 |
| Single householder, w/children | 12.4% | 14.8% | 15.8% |
| Single householder, no children | 28.7% | 10.2% | 10.8% |