| | Caspian, MI | Republic, MI | United States |
| Population | 510 | 591 | 329,725,481 |
| Female Population | 48.8% | 49.8% | 50.5% |
| Male Population | 51.2% | 50.3% | 49.5% |
| Median Age | 52.4 | 53.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 905 | 564 | 309,327,143 |
| Population - 2000 | 997 | 614 | 285,036,114 |
| Population - 1990 | 1,031 | 637 | 251,960,433 |
| Pop. 2000 to Now | -15.3% | -34.7% | 15.6% |
| Pop. 1990 to Now | -18.0% | -37.1% | 30.8% |
| space4 | | | |
| Population Density | 357.4 | 163.4 | 93.4 |
| Land Area | 1.4 | 3.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.3 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Caspian, MI | Republic, MI | United States |
| Age 0 to 4 | 1.4% | 3.9% | 5.9% |
| Age 5 to 9 | 2.9% | 3.2% | 6.1% |
| Age 10 to 14 | 9.4% | 6.6% | 6.6% |
| Age 15 to 17 | 1.8% | 3.7% | 3.9% |
| Age 18 to 20 | 2.2% | 6.3% | 4.0% |
| Age 21 to 24 | 3.1% | 3.7% | 5.2% |
| Age 25 to 34 | 8.8% | 3.9% | 13.8% |
| Age 35 to 44 | 10.2% | 11.3% | 12.9% |
| Age 45 to 54 | 14.7% | 8.5% | 12.6% |
| Age 55 to 59 | 7.3% | 9.3% | 6.7% |
| Age 60 to 64 | 5.7% | 17.6% | 6.3% |
| Age 65 to 74 | 18.2% | 12.0% | 9.6% |
| Age 75 to 84 | 11.4% | 7.6% | 4.5% |
| Age 85 and over | 2.9% | 2.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Caspian, MI | Republic, MI | United States |
| White | 87.6% | 98.5% | 59.4% |
| Black | 3.5% | 0.0% | 12.2% |
| Asian | 1.8% | 0.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.5% | 0.4% |
| Two or More Races | 5.1% | 0.5% | 3.2% |
| Hispanic | 2.0% | 0.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Caspian, MI | Republic, MI | United States |
| Married Population | 43.0% | 47.5% | 49.8% |
| Currently Married | 41.4% | 47.5% | 48.0% |
| Married but Separated | 1.6% | 0.0% | 1.8% |
| Single Population | 57.0% | 52.5% | 50.2% |
| Never Married | 34.3% | 28.8% | 33.8% |
| Divorced | 9.8% | 11.0% | 10.8% |
| Widowed | 13.0% | 12.7% | 5.6% |
| space5 | | | |
| Household Size | 2.03 | 2.15 | 2.60 |
| Households | 251 | 275 | 124,010,992 |
| Family Households | 133 | 164 | 80,755,759 |
| Married couple, w/children | 7.5% | 18.3% | 30.5% |
| Married couple, no children | 54.9% | 50.0% | 42.9% |
| Non Family Households | 118 | 111 | 43,255,233 |
| Single householder, w/children | 27.8% | 12.8% | 15.8% |
| Single householder, no children | 9.8% | 18.9% | 10.8% |