Baseball Crank has begun posting his established win share levels reports for 2009.

In brief, the win share levels use statistical algorithms to analyze each MLB player’s share of his team’s wins:

Win Shares seek to measure a player’s total contribution to a team’s bottom line win/loss record, in the case of non-pitchers through combining batting and fielding contributions. The system makes the assumptions that a team’s total wins can be rationally connected to its runs scored and allowed. Thus, each player is assigned a share of the team’s total wins based on his contribution to scoring and preventing runs.

Baseball Crank produces two numbers. The raw EWSL number for each player identifies a specific rating for data from the the last three years. Raw EWSL reflects past results. The adjusted EWSL number attempts to project the future. This means quantifying an appropriate number for rookies with a starting job, and adjusting for age.

The age adjustments provides one of the most basic parameters for predicting player performance. Before the age of 28 or 29, players tend to improve each year. After 30, they tend to decline. Sometimes dramatically. Individual projections, here as with any expert evaluation, are not that meaningful. But you still have to deal with the odds.