| | Norwich, CT | Marion, IA | United States |
| Population | 40,020 | 41,023 | 329,725,481 |
| Female Population | 51.5% | 53.4% | 50.5% |
| Male Population | 48.5% | 46.6% | 49.5% |
| Median Age | 39.3 | 39.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 40,552 | 35,324 | 309,327,143 |
| Population - 2000 | 36,117 | 26,294 | 285,036,114 |
| Population - 1990 | 37,391 | 20,403 | 251,960,433 |
| Pop. 2000 to Now | 6.9% | 55.1% | 15.6% |
| Pop. 1990 to Now | 3.3% | 99.9% | 30.8% |
| space4 | | | |
| Population Density | 1,426.1 | 2,331.9 | 93.4 |
| Land Area | 28.1 | 17.6 | 3,531,905.4 |
| Water Area | 1.3 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Norwich, CT | Marion, IA | United States |
| Age 0 to 4 | 4.0% | 6.3% | 5.9% |
| Age 5 to 9 | 4.5% | 7.6% | 6.1% |
| Age 10 to 14 | 7.7% | 7.0% | 6.6% |
| Age 15 to 17 | 3.4% | 4.2% | 3.9% |
| Age 18 to 20 | 3.1% | 2.0% | 4.0% |
| Age 21 to 24 | 5.8% | 3.8% | 5.2% |
| Age 25 to 34 | 15.8% | 13.0% | 13.8% |
| Age 35 to 44 | 11.9% | 15.0% | 12.9% |
| Age 45 to 54 | 12.4% | 12.9% | 12.6% |
| Age 55 to 59 | 6.9% | 6.0% | 6.7% |
| Age 60 to 64 | 7.4% | 5.7% | 6.3% |
| Age 65 to 74 | 10.4% | 9.6% | 9.6% |
| Age 75 to 84 | 4.5% | 4.9% | 4.5% |
| Age 85 and over | 2.1% | 2.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Norwich, CT | Marion, IA | United States |
| White | 59.5% | 90.7% | 59.4% |
| Black | 10.2% | 1.9% | 12.2% |
| Asian | 6.8% | 1.8% | 5.6% |
| Native American | 0.3% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.5% | 0.3% | 0.4% |
| Two or More Races | 3.9% | 2.8% | 3.2% |
| Hispanic | 18.8% | 2.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Norwich, CT | Marion, IA | United States |
| Married Population | 42.4% | 56.1% | 49.8% |
| Currently Married | 40.7% | 54.7% | 48.0% |
| Married but Separated | 1.7% | 1.4% | 1.8% |
| Single Population | 57.6% | 43.9% | 50.2% |
| Never Married | 37.7% | 26.0% | 33.8% |
| Divorced | 13.1% | 11.8% | 10.8% |
| Widowed | 6.8% | 6.1% | 5.6% |
| space5 | | | |
| Household Size | 2.34 | 2.45 | 2.60 |
| Households | 16,923 | 16,638 | 124,010,992 |
| Family Households | 10,257 | 10,617 | 80,755,759 |
| Married couple, w/children | 20.8% | 36.0% | 30.5% |
| Married couple, no children | 39.4% | 44.5% | 42.9% |
| Non Family Households | 6,666 | 6,021 | 43,255,233 |
| Single householder, w/children | 24.6% | 14.7% | 15.8% |
| Single householder, no children | 15.2% | 4.8% | 10.8% |