In the county, the population was spread out with 34.20% under the age of 18, 9.80% from 18 to 24, 26.30% from 25 to 44, 19.40% from 45 to 64, and 10.40% who were 65 years of age or older. The median age was 30 years. For every 100 females there were 104.50 males. For every 100 females age 18 and over, there were 102.10 males.. Which age groups living in the county made up less than 20% of the population?