What is the average age of an Olympic athlete?

Usually gymnasts peak around 14 or 15 years old and thus the retirement age comes quickly after. Most gymnasts retire around 19 or 20 years old now-a-days. But it used to be said that 19 was "over-the-hill" for gymnastics. Although, Dominique Dawes retired at 23 years old, just a few months before her 24 birthday. And Russian gymnast Svetlana Khorkina retired at 25 years old.