If you use a Mozilla browser (eg, Firefox) try my player stats search plugin for convenience.
The database has been updated with 2011 offensive stats. Congratulations to Jose Reyes, Shane Victorino, and Dexter Fowler who were among the most dominant triples-hitters last year, and to Miguel Cabrera and Jose Bautista whose on-base percentages were among the most dominant of all time.
6 February 2006
Updated 2 March 2012
The goal here is not to duplicate excellent resources like Total Baseball or The Baseball Encyclopedia, but to take the same data and present it in a way that shows different relationships, yields new insights, and raises new questions. The focus is on putting single season stats in a historical context and identifying the truly outstanding player seasons, not just those with big raw numbers. My method is primarily the z-score (see below for a simple explanation) and a few kinds of charts, all hyperlinked for easy cross-referencing.
There are a few statistics in use on this site that may not be familiar to you. Here are explanations of the least common ones.
- AB/K - At-Bats per Strikeout
- Number of at-bats it takes for player to strike out (AB / SO).
- ISO - Isolated Power
- A measure of ability to get extra base hits (SLG - AVG).
- RC - Runs Created
- An excellent measure originally devised by Bill James to estimate the number of runs a player has contributed to his team through his offensive performance. I use the 2002 version of the formula without situational hitting data.
- SBR - Stolen Base Runs
- A very approximate measure of how many runs a player's basestealing adventures have earned his team (.3*SB - .6*CS).
If there are any other stats you'd like to see on this site please let me know.
What's a Z-Score?
The z-score is a statistical measure of how a particular number compares to the average. Technically it is the number of standard deviations from the mean, but one need not have a complete mathematical understanding of the z-score to appreciate that it shows how a given player performs compared to the competition.
For example, if the league average for home runs is 9 and a player hits exactly 9 home runs, his z-score is zero. If he hits more than 9 HRs his z-score will be positive and if he hits fewer than 9 it will be negative. Precisely how positive and how negative will depend on how other players in the league fared. For example:
- In the National League in 2001 the league average for home runs was about 12. The leaders:
- In the American League in 1920 the league average for home runs was about 4. The leaders:
These two examples deal with some of the most extraordinary numbers of all time, but usually league leaders need not have such high z-scores. Also, certain statistics (like HRs and IBBs) are prone to higher z-scores than others. For example, the z-scores of recent American League OB% leaders:
In short, z-score is a measure of a player's dominance in a given league and season. It allows us to compare players in different eras by quantifying how good they were compared to their competition. It it a useful measure but a relative one, and does not allow us to draw any absolute conclusions like "Babe Ruth was a better home run hitter than Barry Bonds." All we can say is that Ruth was more dominant in his time.
About the Computations
To compute the league stats (mean, maximum, standard deviation, skewness, etc) I have used data from all players with at least 0.5 plate appearances per team game. For appearing on a z-leaderboard or having a season page the minimum is 2.9 plate appearances per team game. I am aware that this is not the conventional minimum to use when calculating leaders, and while I do not think it is the best answer I do believe it is more fair than the conventional cutoffs which reflect the reasonings of their eras. And since this site does not feature conventional leaderboards I hope nobody will be too offended.