Seasonal Age
A player's Seasonal Age is his age in years, as of July 1, of the season in question.
Criticisms of Seasonal Age[edit]
Age, unlike all other numbers used in computations, is truncated to the lower integer, rather than rounded to the closer integer. The result is that when you have to figure out a team's seasonal age, the result will be biased by 6 months.
As an illustration, if you have one player that is 27.60 years old as of July 1, and another player is 28.40 years old as of the same date, the true average as of July 1 should be 28.00. However, the seasonal age format will first truncate 27.60 to 27, and then trucate 28.40 to 28. The average of 27 and 28 is 27.5, a number that is lower than both numbers it is based upon!
The correct action is to not truncate at all, and simply carry the decimal. Otherwise, if truncated is required, then the averaging of the ages should be done prior to truncation.
Because of this issue, some analysts determine the age as current year minus birth year, basically establishing the age as of Dec 31 midnight of the year in question. A player that is 27.60 years old as of July 1, will then be counted as being 28.10 years old, meaning truncated to age 28. A player that is 28.40 years old as of July 1 will then be counted as being 28.90 years old, meaning truncated to age 28. The average of the truncated numbers is 28.0. In short, in order to counteract the bias of 0.5 years from the truncation-then-average of the seasonal age process, you add 0.5 years first prior to truncation.
The benefit is that you only need to know the birth year of the player, rather than also know whether he was born before or after July 1.
