| | Ann Arbor, MI | Acton, MA | United States |
| Population | 122,731 | 23,899 | 329,725,481 |
| Female Population | 50.7% | 53.0% | 50.5% |
| Male Population | 49.3% | 47.0% | 49.5% |
| Median Age | 27.5 | 43.5 | 38.4 |
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| Population - 2010 | 114,197 | 21,983 | 309,327,143 |
| Population - 2000 | 114,024 | 20,331 | 285,036,114 |
| Population - 1990 | 109,592 | 17,872 | 251,960,433 |
| Pop. 2000 to Now | 4.6% | 15.6% | 15.6% |
| Pop. 1990 to Now | 8.8% | 31.5% | 30.8% |
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| Population Density | 4,398.5 | 1,203.1 | 93.4 |
| Land Area | 27.9 | 19.9 | 3,531,905.4 |
| Water Area | 0.9 | 0.4 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Ann Arbor, MI | Acton, MA | United States |
| Age 0 to 4 | 3.9% | 4.6% | 5.9% |
| Age 5 to 9 | 3.4% | 6.9% | 6.1% |
| Age 10 to 14 | 3.3% | 7.6% | 6.6% |
| Age 15 to 17 | 2.1% | 6.9% | 3.9% |
| Age 18 to 20 | 14.4% | 2.6% | 4.0% |
| Age 21 to 24 | 17.4% | 3.3% | 5.2% |
| Age 25 to 34 | 17.4% | 6.8% | 13.8% |
| Age 35 to 44 | 10.2% | 14.1% | 12.9% |
| Age 45 to 54 | 7.8% | 17.5% | 12.6% |
| Age 55 to 59 | 3.7% | 9.1% | 6.7% |
| Age 60 to 64 | 4.4% | 4.7% | 6.3% |
| Age 65 to 74 | 6.9% | 9.2% | 9.6% |
| Age 75 to 84 | 3.5% | 4.3% | 4.5% |
| Age 85 and over | 1.5% | 2.4% | 1.9% |
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| Race | | | |
| | Ann Arbor, MI | Acton, MA | United States |
| White | 67.5% | 63.4% | 59.4% |
| Black | 6.5% | 4.2% | 12.2% |
| Asian | 16.6% | 23.6% | 5.6% |
| Native American | 0.3% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.3% | 0.5% | 0.4% |
| Two or More Races | 4.2% | 4.7% | 3.2% |
| Hispanic | 4.6% | 3.5% | 18.4% |
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| Marriage & Family | | | |
| | Ann Arbor, MI | Acton, MA | United States |
| Married Population | 34.8% | 63.3% | 49.8% |
| Currently Married | 34.4% | 63.0% | 48.0% |
| Married but Separated | 0.4% | 0.3% | 1.8% |
| Single Population | 65.2% | 36.7% | 50.2% |
| Never Married | 56.5% | 25.4% | 33.8% |
| Divorced | 6.3% | 6.6% | 10.8% |
| Widowed | 2.4% | 4.6% | 5.6% |
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| Household Size | 2.21 | 2.66 | 2.60 |
| Households | 49,661 | 8,931 | 124,010,992 |
| Family Households | 21,748 | 6,643 | 80,755,759 |
| Married couple, w/children | 31.0% | 46.5% | 30.5% |
| Married couple, no children | 50.1% | 40.1% | 42.9% |
| Non Family Households | 27,913 | 2,288 | 43,255,233 |
| Single householder, w/children | 9.6% | 8.3% | 15.8% |
| Single householder, no children | 9.3% | 5.0% | 10.8% |