| | Gayville, SD | Avon, SD | United States |
| Population | 388 | 735 | 329,725,481 |
| Female Population | 45.6% | 47.4% | 50.5% |
| Male Population | 54.4% | 52.7% | 49.5% |
| Median Age | 48.5 | 36.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 405 | 590 | 309,327,143 |
| Population - 2000 | 418 | 561 | 285,036,114 |
| Population - 1990 | 401 | 576 | 251,960,433 |
| Pop. 2000 to Now | -7.4% | 4.1% | 15.6% |
| Pop. 1990 to Now | -3.5% | 1.4% | 30.8% |
| space4 | | | |
| Population Density | 1,892.7 | 1,137.8 | 93.4 |
| Land Area | 0.2 | 0.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Gayville, SD | Avon, SD | United States |
| Age 0 to 4 | 5.2% | 4.4% | 5.9% |
| Age 5 to 9 | 5.2% | 7.5% | 6.1% |
| Age 10 to 14 | 5.4% | 16.9% | 6.6% |
| Age 15 to 17 | 2.1% | 6.3% | 3.9% |
| Age 18 to 20 | 1.3% | 1.2% | 4.0% |
| Age 21 to 24 | 1.3% | 1.5% | 5.2% |
| Age 25 to 34 | 16.8% | 10.1% | 13.8% |
| Age 35 to 44 | 9.0% | 12.0% | 12.9% |
| Age 45 to 54 | 11.6% | 6.9% | 12.6% |
| Age 55 to 59 | 7.0% | 7.2% | 6.7% |
| Age 60 to 64 | 13.7% | 6.7% | 6.3% |
| Age 65 to 74 | 14.9% | 12.0% | 9.6% |
| Age 75 to 84 | 4.4% | 4.8% | 4.5% |
| Age 85 and over | 2.3% | 2.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Gayville, SD | Avon, SD | United States |
| White | 83.8% | 94.4% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 0.0% | 0.0% | 5.6% |
| Native American | 1.0% | 2.9% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 2.1% | 0.5% | 3.2% |
| Hispanic | 13.1% | 2.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Gayville, SD | Avon, SD | United States |
| Married Population | 51.4% | 67.9% | 49.8% |
| Currently Married | 49.8% | 66.4% | 48.0% |
| Married but Separated | 1.5% | 1.5% | 1.8% |
| Single Population | 48.6% | 32.1% | 50.2% |
| Never Married | 21.1% | 25.0% | 33.8% |
| Divorced | 16.5% | 1.3% | 10.8% |
| Widowed | 11.0% | 5.7% | 5.6% |
| space5 | | | |
| Household Size | 2.06 | 2.70 | 2.60 |
| Households | 188 | 272 | 124,010,992 |
| Family Households | 115 | 188 | 80,755,759 |
| Married couple, w/children | 16.5% | 26.1% | 30.5% |
| Married couple, no children | 53.0% | 64.4% | 42.9% |
| Non Family Households | 73 | 84 | 43,255,233 |
| Single householder, w/children | 3.5% | 8.0% | 15.8% |
| Single householder, no children | 27.0% | 1.6% | 10.8% |