Boulder's population is younger than the national average, largely due to the presence of university students. The median age at the 2010 census was 28.7 years compared to the U.S. median of 37.2 years. In Boulder, 13.9% of the residents were younger than the age of 18, 29.1% from 18 to 24, 27.6% from 25 to 44, 20.3% from 45 to 64, and 8.9% were 65 years of age or older. For every 100 females, there were 105.5 males. For every 100 females age 18 and older, there were 106.2 males.