10 for 10: #4 Win Expectancy and Run Expectancy
Posted by Sean Forman on March 26, 2010
This is the fourth of ten features we are adding for our 10th anniversary.
The first place I saw Win Expectancy (WE) was when I was writing for the Big Baseball Annual back in the late 1990's. Doug Drinen, who has since moved on to become one of the leading NFL analysts and creator of Pro-Football-Reference.com, wrote a series of articles on reliever usage that built on the original Mills Brothers work on Win Expectancy (WE). Doug even included a WS Game WE Graph in one of the books. I always have thought it was an elegant measurement of what happened during the game and I'm excited to now have it on the site.
Tom Tango was very helpful in working out the details for implementation. His run environment adjusted numbers for Win Expectancy, Leverage, Base-Out Run Expectancy and Base-Out Leverage are the basis for the numbers you see on the site.
A quick rundown of what is on the site. WE and RE appear for seasons for which we have play-by-play, 1952-2009. The data is only 100% complete for 1974-present. For the earlier seasons, we are missing some games for each season. A full listing of our coverage is here.
- The More Stats sections for pitchers and hitters have tables with Win Expectancy, Run Expectancy and Pitching and Batting Runs and Wins (Jack Morris / Mike Schmidt). This chart has four wins-based metrics, batting or pitching Wins, WPA, WPA/LI, and REW.
- All Regular Season Box Scores for which we have PBP have interactive WE Charts. (Tigers @ Twins Playoff Game / Tutorial Video highlighting the features on the chart)
- These stats also now appear on player gamelog pages.
- Team Detailed/More Stats (link just above the team batting stats) pages have full team Win Probability, RE24, and Batting and Pitching Wins statistics. (1979 Pirates Batting / 2001 D'Backs Pitching)
- 1952-Present League Pages have complete RE and WE registers. Select Win Probability from the list of options in the nav bar just above the league batting stats. (2007 NL Pitching / 1980 MLB Batting)
- Leaderboards for these stats have been added to yearly league pages (2009 NL Pitching), team all-time leaderboards (Mets Batting Leaders), and the leaders section (All-Time Pitching Wins / Year-by-Year Pitching REW).
- I've created a full (perhaps even tedious) rundown of the method used to create these stats and the specific stats provided. Please let me know if you have any questions or complaints.
- This data is integrated with the Play Index, so you can now find things like:
- Greatest Amount of WPA by Reliever from 1980-2009
- Greatest RE24 for a Second Baseman in a season since 1952
- Longest Streak of High Leverage (aLI > 2.00) for a Pitcher
- Most Games in a season in the last decade with RE24 ≤ 0
- Highest WPA games of 2009 for hitters
- Highest Seasonal WPA with REW ≤ 0.00 for a Pitcher
I hope you are enjoying these improvements to the site as much as I'm enjoying putting them together. Be sure to three earlier features as well. Questions and comments are always welcome. I'm hoping update #5 will come next week, but given the onrushing advance of Opening Day it may occur after first pitch.
ERA+ update: yesterday, I mentioned that we erroneously changed the definition for ERA+. I am still considering a long-term change, but for the short-term have changed it back. I apologize for the confusion.
March 26th, 2010 at 12:53 pm
Oh, cool. Can I do something like get the LI of all saves in a given year?
March 26th, 2010 at 3:42 pm
This is great, great stuff. Searching out these stats with PI makes them far more useful for historical research than they have ever been at any other site. Who would have realized that in the top 4 Mets pitchers in career WPA for the team, along with Seaver, Koosman and Gooden you would also find Armando Benitez?
There will be some oddites along the way with the manner baserunning is treated for WPA purposes. Just looking at some random Mets boxscores, here's one: http://www.baseball-reference.com/boxes/NYN/NYN196204280.shtml. That's the Mets'second win in franchise history. The most valuable performer for the Mets in this game, as calculated by most WPA, is shown to be John DeMerit. DeMerit was in the game solely as a punch runner -- entered the game as a PR at first base, moved to second on a walk, moved to third on a ground out toward first base and scored on a wild pitch. Demerit gets .294 WPA for that sequence, more than any other Met netted in that game, which the Mets won 8-6. The crediting of wild pitches may need to be re-thought. Does the base runner really deserve WPA credit for a wild pitch? Maybe the batter, whose talents were perhaps sufficently impressive that the pitcher risked a wild pitch, deserves the credit more than the runner?
March 26th, 2010 at 3:52 pm
Ah, typos. Pinch runner, of course, not punch runner. That's Pete Rose in this game: http://www.baseball-reference.com/boxes/NYN/NYN197310080.shtml
March 26th, 2010 at 6:48 pm
Is the batting runs/wins thing new to PI as well, or did I just not notice it before?
COOL.
March 26th, 2010 at 7:22 pm
It's new as well
March 27th, 2010 at 7:25 am
Sean, Thanks for putting batting runs in as a sortable stat., it's much appreciated. I'm thinking there's more information on Baseball Reference than the rest of the internet combined!! Fantastic site for us Baseball nuts.
March 27th, 2010 at 11:51 am
So which of these new stats is the most important in determining the player's worth to the club during a game and/or during a season?
March 29th, 2010 at 12:31 pm
Dave, I don't think there's an easy answer to that. They sort of measure different things, or they measure similar things in different ways. I don't think any is "most important" but you might look at different numbers depending on the question you're trying to answer, or look at all of them to get different perspectives on the player's performance/value.
March 29th, 2010 at 1:50 pm
What are the differences between the WPA here compared to the numbers over at fangraphs.com?
March 29th, 2010 at 2:05 pm
Bill,
Please read the about page.
http://bbref.com/about/wpa.shtml
I am not 100% certain, but I'm fairly certain it relates to differing run environments used.
March 31st, 2010 at 10:37 am
Thanks for clearing that up Sean!
April 3rd, 2010 at 7:52 am
[...] Now that WPA is widely available on Baseball-Reference.com, it's time to start using it. I feel it is perhaps the most useful stat around today. If you're not familiar with the stat, check out Sean's post announcing this addition. [...]
April 7th, 2010 at 11:48 am
[...] thought I'd go ahead and research this a bit more, using Win Expectancy [...]