In the county, the population was spread out with 23.20% under the age of 18, 7.70% from 18 to 24, 27.00% from 25 to 44, 28.00% from 45 to 64, and 14.10% who were 65 years of age or older.  The median age was 40 years. For every 100 females, there were 97.00 males.  For every 100 females age 18 and over, there were 96.40 males.. Which age group has the least population?