Baseball Graphs is dedicated to the better use and communication of baseball statistics. Below, you'll find excerpts from, and links to, some of the best baseball writers on the Internet. Follow the links above to read my own intermittent attempts at wisdom (the Baseball Graphs blog), and the heart of this site, historical graphs of every season dating back to 1900.
There are also two special sections you might want to check out. One is the graphical review of the 2003 season, which informed our work at The Hardball Times. The other is the Batted Balls Library, which includes a unique look at batters and pitchers from 2002 through 2005.
Tangotiger invented a statistic called Leveraged Index (or Crucial Innings), which basically rates the relative importance of a pitcher’s innings. Tango developed his Leveraged Index by assessing the potential game impact of each relief pitcher’s appearance using a method called Win Expectancy, which requires play-by-play data.
Bill James attempted to estimate the same thing in Win Shares, but historical play-by-play data doesn’t exist. So Bill created an estimate by weighting the number of save opportunities and holds that each pitcher had. He called them Save-Equivalent Innings.
I’ve actually changed Bill’s formula a bit, because I think the original formula overstated the impact of saves and holds in today’s save-happy environment. The specific formula I use is 1.5 times Saves plus .5 times Holds. This creates Save-Equivalent Innings. I then go ahead and create my own Index via this formula:
(IP + Save-Equivalent Innings)/IP
The formula maxes out at 1.9, which is also consistent with James’ approach and Tango’s general findings. Here are the links to the sortable Save-Equivalent Index listings:
American League
National League