| | Billerica, MA | Vacaville, CA | United States |
| Population | 41,995 | 102,256 | 329,725,481 |
| Female Population | 49.1% | 47.9% | 50.5% |
| Male Population | 50.9% | 52.2% | 49.5% |
| Median Age | 43 | 37.8 | 38.4 |
| space3 | | | |
| Population - 2010 | 40,419 | 92,530 | 309,327,143 |
| Population - 2000 | 38,981 | 88,625 | 285,036,114 |
| Population - 1990 | 37,609 | 71,479 | 251,960,433 |
| Pop. 2000 to Now | 10.4% | 14.3% | 15.6% |
| Pop. 1990 to Now | 14.4% | 41.8% | 30.8% |
| space4 | | | |
| Population Density | 1,642.6 | 3,499.4 | 93.4 |
| Land Area | 25.6 | 29.2 | 3,531,905.4 |
| Water Area | 0.7 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Billerica, MA | Vacaville, CA | United States |
| Age 0 to 4 | 4.0% | 5.9% | 5.9% |
| Age 5 to 9 | 4.4% | 6.7% | 6.1% |
| Age 10 to 14 | 5.5% | 5.8% | 6.6% |
| Age 15 to 17 | 4.1% | 3.6% | 3.9% |
| Age 18 to 20 | 2.8% | 3.2% | 4.0% |
| Age 21 to 24 | 4.7% | 5.2% | 5.2% |
| Age 25 to 34 | 14.4% | 15.6% | 13.8% |
| Age 35 to 44 | 12.9% | 13.7% | 12.9% |
| Age 45 to 54 | 15.2% | 12.7% | 12.6% |
| Age 55 to 59 | 8.7% | 6.8% | 6.7% |
| Age 60 to 64 | 7.1% | 6.4% | 6.3% |
| Age 65 to 74 | 10.1% | 9.0% | 9.6% |
| Age 75 to 84 | 4.3% | 4.0% | 4.5% |
| Age 85 and over | 1.7% | 1.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Billerica, MA | Vacaville, CA | United States |
| White | 79.6% | 48.3% | 59.4% |
| Black | 6.2% | 9.2% | 12.2% |
| Asian | 7.2% | 8.8% | 5.6% |
| Native American | 0.0% | 0.4% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.7% | 0.2% |
| Other | 0.6% | 0.3% | 0.4% |
| Two or More Races | 1.9% | 6.6% | 3.2% |
| Hispanic | 4.3% | 25.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Billerica, MA | Vacaville, CA | United States |
| Married Population | 52.8% | 50.9% | 49.8% |
| Currently Married | 51.3% | 48.9% | 48.0% |
| Married but Separated | 1.5% | 2.1% | 1.8% |
| Single Population | 47.2% | 49.1% | 50.2% |
| Never Married | 33.4% | 33.3% | 33.8% |
| Divorced | 8.9% | 10.9% | 10.8% |
| Widowed | 4.9% | 4.9% | 5.6% |
| space5 | | | |
| Household Size | 2.63 | 2.84 | 2.60 |
| Households | 15,498 | 33,457 | 124,010,992 |
| Family Households | 11,352 | 24,423 | 80,755,759 |
| Married couple, w/children | 33.2% | 31.7% | 30.5% |
| Married couple, no children | 44.2% | 43.9% | 42.9% |
| Non Family Households | 4,146 | 9,034 | 43,255,233 |
| Single householder, w/children | 7.2% | 13.5% | 15.8% |
| Single householder, no children | 15.5% | 10.9% | 10.8% |