In the county, the population was spread out with 21.7% under the age of 18,  8.5% from 18 to 24, 26.9% from 25 to 44, 27.7% from 45 to 64, and 15.0% who were 65 years of age or older. The median age was 40 years. For every 100 females, there were 94.4 males. For every 100 females age 18 and over, there were 98.7 males.. How many years is the age span for the group with the smallest percentage of the counties population?