A seemingly intrinsic part of the game of baseball is the keeping of statistics on the achievements of the players. Started by Henry Chadwick in the 19th century who devised the concept of batting average based on his experience of cricket. Commonly used statistics are explained here:
... 25 to 44, 21.9% from 45 to 64, and 16.9% who are 65 years of age or older. The median age is 39 years. For every 100 females there are 113.3 males. For every 100 ...