| Underhill - Population Change | FIPS Code=07075 |
| Absolute Population Change, 1970-1980 | 974 |
| Per Cent Population Change, 1970-1980 | 81.30 |
| Absolute Population Change, 1980-1990 | 627 |
| Per Cent Population Change, 1980-1990 | 28.87 |
| Population Estimate, 1996 | 2900 |
| Population Estimate, 2000 | 3901 |
| Population Estimate, 2005 | 4511 |
| Population Estimate, 2010 | 5030 |
| Population Estimate, 2015 | 5624 |
| Absolute Population Change, 1990-1996 | 101 |
| Per Cent Population Change, 1990-1996 | 3.61 |
| Absolute Population Change, 1996-2005 | 1611 |
| Per Cent Population Change, 1996-2005 | 55.55 |
| Absolute Population Change, 2005-2015 | 1113 |
| Per Cent Population Change, 2005-2015 | 24.67 |