In the county, the population was spread out with 23.70% under the age of 18, 15.50% from 18 to 24, 26.50% from 25 to 44, 21.80% from 45 to 64, and 12.50% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 93.50 males. For every 100 females age 18 and over, there were 90.00 males.. Which age group was least common in the county?