| | Ludlow, MA | Fairfield, ID | United States |
| Population | 21,050 | 493 | 329,725,481 |
| Female Population | 48.0% | 66.7% | 50.5% |
| Male Population | 52.0% | 33.3% | 49.5% |
| Median Age | 45.8 | 35.5 | 38.4 |
| space3 | | | |
| Population - 2010 | 21,136 | 415 | 309,327,143 |
| Population - 2000 | 21,209 | 395 | 285,036,114 |
| Population - 1990 | 18,820 | 371 | 251,960,433 |
| Pop. 2000 to Now | -0.5% | 2.0% | 15.6% |
| Pop. 1990 to Now | 12.1% | 8.6% | 30.8% |
| space4 | | | |
| Population Density | 773.8 | 562.8 | 93.4 |
| Land Area | 27.2 | 0.9 | 3,531,905.4 |
| Water Area | 1.1 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Ludlow, MA | Fairfield, ID | United States |
| Age 0 to 4 | 2.6% | 4.5% | 5.9% |
| Age 5 to 9 | 5.9% | 15.0% | 6.1% |
| Age 10 to 14 | 3.9% | 8.5% | 6.6% |
| Age 15 to 17 | 3.3% | 3.0% | 3.9% |
| Age 18 to 20 | 3.2% | 4.3% | 4.0% |
| Age 21 to 24 | 6.0% | 0.0% | 5.2% |
| Age 25 to 34 | 11.9% | 13.6% | 13.8% |
| Age 35 to 44 | 12.7% | 29.0% | 12.9% |
| Age 45 to 54 | 14.4% | 5.1% | 12.6% |
| Age 55 to 59 | 7.1% | 4.7% | 6.7% |
| Age 60 to 64 | 8.4% | 2.8% | 6.3% |
| Age 65 to 74 | 12.2% | 2.4% | 9.6% |
| Age 75 to 84 | 5.2% | 6.3% | 4.5% |
| Age 85 and over | 3.2% | 0.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Ludlow, MA | Fairfield, ID | United States |
| White | 85.1% | 93.3% | 59.4% |
| Black | 1.6% | 0.0% | 12.2% |
| Asian | 1.1% | 0.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 2.5% | 2.6% | 3.2% |
| Hispanic | 9.7% | 4.1% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Ludlow, MA | Fairfield, ID | United States |
| Married Population | 51.2% | 28.2% | 49.8% |
| Currently Married | 49.4% | 28.2% | 48.0% |
| Married but Separated | 1.9% | 0.0% | 1.8% |
| Single Population | 48.8% | 71.8% | 50.2% |
| Never Married | 32.5% | 26.5% | 33.8% |
| Divorced | 10.2% | 41.4% | 10.8% |
| Widowed | 6.0% | 3.9% | 5.6% |
| space5 | | | |
| Household Size | 2.36 | 4.07 | 2.60 |
| Households | 8,567 | 121 | 124,010,992 |
| Family Households | 6,035 | 54 | 80,755,759 |
| Married couple, w/children | 17.7% | 51.9% | 30.5% |
| Married couple, no children | 55.6% | 37.0% | 42.9% |
| Non Family Households | 2,532 | 67 | 43,255,233 |
| Single householder, w/children | 12.9% | 11.1% | 15.8% |
| Single householder, no children | 13.8% | 0.0% | 10.8% |