The List of Conservation topics is a link page for the conservation of both the natural environment and the built environment. There are four sections so far:
... under the age of 18, 6.2% from 18 to 24, 17.7% from 25 to 44, 36.0% from 45 to 64, and 12.5% who are 65 years of age or older. The median age is 44 years. For every 100 ...