| | Millbury, MA | Port St. Lucie, FL | United States |
| Population | 13,827 | 202,177 | 329,725,481 |
| Female Population | 52.5% | 50.8% | 50.5% |
| Male Population | 47.5% | 49.3% | 49.5% |
| Median Age | 43.9 | 42.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 13,270 | 164,860 | 309,327,143 |
| Population - 2000 | 12,784 | 88,769 | 285,036,114 |
| Population - 1990 | 12,228 | 57,058 | 251,960,433 |
| Pop. 2000 to Now | 9.3% | 136.3% | 15.6% |
| Pop. 1990 to Now | 14.3% | 267.6% | 30.8% |
| space4 | | | |
| Population Density | 880.3 | 1,696.3 | 93.4 |
| Land Area | 15.7 | 119.2 | 3,531,905.4 |
| Water Area | 0.7 | 1.6 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Millbury, MA | Port St. Lucie, FL | United States |
| Age 0 to 4 | 4.7% | 5.3% | 5.9% |
| Age 5 to 9 | 5.9% | 5.8% | 6.1% |
| Age 10 to 14 | 4.6% | 6.7% | 6.6% |
| Age 15 to 17 | 4.5% | 3.9% | 3.9% |
| Age 18 to 20 | 2.0% | 2.8% | 4.0% |
| Age 21 to 24 | 3.7% | 4.1% | 5.2% |
| Age 25 to 34 | 13.0% | 12.2% | 13.8% |
| Age 35 to 44 | 12.6% | 12.4% | 12.9% |
| Age 45 to 54 | 15.0% | 13.1% | 12.6% |
| Age 55 to 59 | 10.5% | 6.7% | 6.7% |
| Age 60 to 64 | 5.4% | 6.8% | 6.3% |
| Age 65 to 74 | 10.9% | 11.5% | 9.6% |
| Age 75 to 84 | 4.9% | 7.1% | 4.5% |
| Age 85 and over | 2.3% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Millbury, MA | Port St. Lucie, FL | United States |
| White | 88.0% | 54.6% | 59.4% |
| Black | 1.4% | 17.3% | 12.2% |
| Asian | 3.9% | 2.0% | 5.6% |
| Native American | 0.2% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.2% | 0.0% | 0.2% |
| Other | 0.6% | 0.5% | 0.4% |
| Two or More Races | 3.9% | 3.6% | 3.2% |
| Hispanic | 1.9% | 21.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Millbury, MA | Port St. Lucie, FL | United States |
| Married Population | 50.3% | 53.1% | 49.8% |
| Currently Married | 49.4% | 51.8% | 48.0% |
| Married but Separated | 0.9% | 1.3% | 1.8% |
| Single Population | 49.7% | 46.9% | 50.2% |
| Never Married | 31.1% | 27.9% | 33.8% |
| Divorced | 13.2% | 12.9% | 10.8% |
| Widowed | 5.5% | 6.1% | 5.6% |
| space5 | | | |
| Household Size | 2.65 | 2.81 | 2.60 |
| Households | 5,165 | 71,609 | 124,010,992 |
| Family Households | 3,722 | 53,535 | 80,755,759 |
| Married couple, w/children | 30.9% | 28.4% | 30.5% |
| Married couple, no children | 44.6% | 45.5% | 42.9% |
| Non Family Households | 1,443 | 18,074 | 43,255,233 |
| Single householder, w/children | 12.5% | 14.8% | 15.8% |
| Single householder, no children | 12.0% | 11.3% | 10.8% |