As of April 2007, there were 77,465 people living in Allen. This is a dramatic increase from the city's 2000 Census figures showing just over 40,000 people, 14,205 households, and 12,045 families. Other statistics, based on 2000 Census figures, showed population density at 638.4/km² (1,653.6/sq mi). There were 15,227 housing units at an average density of 578.1/sq mi (223.2/km²). The racial makeup of the city was 87.14% White, 4.40% African American, 0.52% Native American, 3.73% Asian, 0.05% Pacific Islander, 2.41% from other races, and 1.75% from two or more races. Hispanic or Latino of any race were 6.98% of the population.
There were 14,205 households out of which 55.5% had children under the age of 18 living with them, 74.6% were married couples living together, 7.4% had a female householder with no husband present, and 15.2% were non-families. 11.9% of all households were made up of individuals and 1.6% had someone living alone who was 65 years of age or older. The average household size was 3.07 and the average family size was 3.35.
In the city the population was spread out with 34.9% under the age of 18, 5.4% from 18 to 24, 40.7% from 25 to 44, 16.2% from 45 to 64, and 2.8% who were 65 years of age or older. The median age was 31 years. For every 100 females there were 99.7 males. For every 100 females age 18 and over, there were 97.3 males.
The median income for a household in the city in 2007 was $93,392, and the median income for a family was $100,736.