| | Greene, IA | Clear Lake, IA | United States |
| Population | 1,154 | 7,673 | 329,725,481 |
| Female Population | 53.1% | 52.8% | 50.5% |
| Male Population | 46.9% | 47.2% | 49.5% |
| Median Age | 55 | 52.3 | 38.4 |
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| Population - 2010 | 1,130 | 7,777 | 309,327,143 |
| Population - 2000 | 1,099 | 8,161 | 285,036,114 |
| Population - 1990 | 1,142 | 8,183 | 251,960,433 |
| Pop. 2000 to Now | -3.6% | -7.9% | 15.6% |
| Pop. 1990 to Now | -7.3% | -8.1% | 30.8% |
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| Population Density | 1,015.9 | 710.7 | 93.4 |
| Land Area | 1.1 | 10.8 | 3,531,905.4 |
| Water Area | 0.1 | 2.6 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Greene, IA | Clear Lake, IA | United States |
| Age 0 to 4 | 4.4% | 4.0% | 5.9% |
| Age 5 to 9 | 1.8% | 3.8% | 6.1% |
| Age 10 to 14 | 5.9% | 5.3% | 6.6% |
| Age 15 to 17 | 2.4% | 4.0% | 3.9% |
| Age 18 to 20 | 1.7% | 4.8% | 4.0% |
| Age 21 to 24 | 1.4% | 3.3% | 5.2% |
| Age 25 to 34 | 17.0% | 7.9% | 13.8% |
| Age 35 to 44 | 5.7% | 9.6% | 12.9% |
| Age 45 to 54 | 9.6% | 11.6% | 12.6% |
| Age 55 to 59 | 4.4% | 8.2% | 6.7% |
| Age 60 to 64 | 11.0% | 10.4% | 6.3% |
| Age 65 to 74 | 12.5% | 16.7% | 9.6% |
| Age 75 to 84 | 12.7% | 6.4% | 4.5% |
| Age 85 and over | 9.4% | 4.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Greene, IA | Clear Lake, IA | United States |
| White | 90.1% | 91.2% | 59.4% |
| Black | 0.0% | 0.3% | 12.2% |
| Asian | 5.6% | 3.8% | 5.6% |
| Native American | 0.3% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.4% | 1.3% | 3.2% |
| Hispanic | 3.5% | 3.3% | 18.4% |
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| Marriage & Family | | | |
| | Greene, IA | Clear Lake, IA | United States |
| Married Population | 56.7% | 52.2% | 49.8% |
| Currently Married | 53.5% | 51.2% | 48.0% |
| Married but Separated | 3.3% | 1.0% | 1.8% |
| Single Population | 43.3% | 47.8% | 50.2% |
| Never Married | 26.1% | 25.3% | 33.8% |
| Divorced | 6.6% | 15.7% | 10.8% |
| Widowed | 10.6% | 6.8% | 5.6% |
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| Household Size | 2.02 | 2.14 | 2.60 |
| Households | 561 | 3,480 | 124,010,992 |
| Family Households | 382 | 2,067 | 80,755,759 |
| Married couple, w/children | 5.8% | 23.3% | 30.5% |
| Married couple, no children | 64.4% | 56.7% | 42.9% |
| Non Family Households | 179 | 1,413 | 43,255,233 |
| Single householder, w/children | 14.7% | 11.5% | 15.8% |
| Single householder, no children | 15.2% | 8.5% | 10.8% |