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SRS Calculation Details

Posted by Mike Lynch on March 3, 2015

One of the more common subjects for queries we receive at Sports-Reference is our SRS (Simple Rating System) figures. For some background, the first of our sites to add SRS was Pro-Football-Reference, when Doug Drinen added it to the site in 2006 and provided this excellent primer. The important thing to know is that SRS is a rating that takes into account average point differential and strength of schedule. For instance, the 2006-07 Spurs won games by an average of 8.43 points per game and played a schedule with opponents that were 0.08 points worse than average, giving them an SRS of 8.35. This means they were 8.35 points better than an average team. An average team would have an SRS of 0.0. The calculation can be complicated, but the premise is simple and it produces easily interpreted results.

However, there are some variations in the way we calculate SRS across our various sites. We'll break down these differences below.

Pro-Football-Reference.com SRS: PFR's SRS is unique in that a home-field advantage is included as a part of the calculation because of the short schedule compared to the other sports (we don't want a team to look relatively weak at the halfway point because they've only played 3 of their first 8 at home, for instance). This HFA fluctuates yearly based on game results, but it is generally somewhere between 2 and 3 points (2006 being an outlier, as you'll see). Below is a look at the HFA numbers we have used since 2001. If you'd like to calculate these HFAs yourself, just sum up every team's home point differential and then divide by the total number of games played across the league that season. This data can easily be found in the Play Index for each season:

  • 2001: 2.0081
  • 2002: 2.2461
  • 2003: 3.5547
  • 2004: 2.5078
  • 2005: 3.6484
  • 2006: 0.8477
  • 2007: 2.8672
  • 2008: 2.5586
  • 2009: 2.2070
  • 2010: 1.8945
  • 2011: 3.2656
  • 2012: 2.4336
  • 2013: 3.1055
  • 2014: 2.4883

College Football SRS: Our CFB SRS does not contain a home-field advantage element, but it does have some other quirks. Most importantly, we have capped the margin of victory considered for the formula. Due to the number of mismatches seen in college football, the maximum point differential a team can be credited with in a game is 24. We also credit all wins as a minimum of plus-7 margin of victory (so if you win by 1 point, it's treated the same as a 7-point win). The same logic is applied to losses, as well. One other wrinkle for CFB is that all non-major opponents are included as one team for the sake of the ratings.

College Basketball SRS: SRS for college hoops is straight forward (no HFA & no adjusted MOV), but one item to note is that games against non-major opponents are not counted in our calculations.

MLB, NBA & NHL: All of these SRS calculations are straight forward with no adjustments for HFA and no capping of MOV. It should be noted, however, that no special consideration is given for extra-innings, overtimes or shootouts, either.

We'll close with a quick rundown of the various merits and weaknesses of SRS, from Drinen's original 2006 post. These bullet points were created to describe the system used for NFL SRS, but many of the strengths and weaknesses can applied to the other sports, as well:

  • The numbers it spits out are easy to interpret - if Team A's rating is 3 bigger than Team B's, this means that the system thinks Team A is 3 points better than Team B. With most ranking algorithms, the numbers that come out have no real meaning that can be translated into an English sentence. With this system, the units are easy to understand.
  • It is a predictive system rather than a retrodictive system - this is a very important distinction. You can use these ratings to answer the question: which team is stronger? I.e. which team is more likely to win a game tomorrow? Or you can use them to answer the question: which of these teams accomplished more in the past? Some systems answer the first questions more accurately; they are called predictive systems. Others answer the latter question more accurately; they are called retrodictive systems. As it turns out, this is a pretty good predictive system. For the reasons described below, it is not a good retrodictive system.
  • It weights all games equally - every football fan knows that the Colts' week 17 game against Arizona was a meaningless exhibition, but the algorithm gives it the same weight as all the rest of the games.
  • It weights all points equally, and therefore ignores wins and losses - take a look at the Colts season. If you take away 10 points in week 3 and give them back 10 points in week 4, you've just changed their record, but you haven't changed their rating at all. If you take away 10 points in week 3 and give back 20 points in week 4, you have made their record worse but their rating better. Most football fans put a high premium on the few points that move you from a 3-point loss to a 3-point win and almost no weight on the many points that move you from a 20-point win to a 50-point win.
  • It is easily impressed by blowout victories - this system thinks a 50-point win and a 10-point loss is preferable to two 14-point wins. Most fans would disagree with that assessment.
  • It is slightly biased toward offensive-minded teams - because it considers point margins instead of point ratios, it treats a 50-30 win as more impressive than a 17-0 win. Again, this is an assessment that most fans would disagree with.
  • This should go without saying, but - I'll say it anyway. The system does not take into account injuries, weather conditions, yardage gained, the importance of the game, whether it was a Monday Night game or not, whether the quarterback's grandmother was sick, or anything else besides points scored and points allowed.

 

2 Comments | Posted in Announcement, Baseball-Reference.com, Basketball-Reference.com, CBB at Sports Reference, CFB at Sports Reference, Data, FAQ, Features, Hockey-Reference.com, Pro-Football-Reference.com, SRS, Stat Questions, Statgeekery, Uncategorized

Winter League Statistics Added

Posted by Mike Lynch on February 6, 2015

We have recently added Cuban statistics and Arizona Fall League stats. Our other new addition is statistics for the Dominican, Venezuelan, Puerto Rican & Mexican Pacific Winter Leagues.

These leagues can all be accessed via our Minor Leagues section. On player's minors pages, the abbreviations are DOWL (Dominican), VEWL (Venezuelan), PRWL (Puerto Rican) & MXPW (Mexican Pacific). These leagues also feature batting leaderboards, so you can find outstanding performances like Kendrys Morales batting .404, and pitching leaderboards.

Comments Off | Posted in Announcement, Baseball-Reference.com, Data

Arizona Fall League Stats Added to Baseball-Reference

Posted by Mike Lynch on February 6, 2015

Yesterday we announced that we have added Cuban statistics to the site. Today, we are happy to announce that we have added Arizona Fall League statistics to the site from 2005-13 (with 2014 coming soon).

Statistics from this league can be seen on a player's minor league page. Here is Mike Trout's,  for instance. The Arizona Fall League is coded as AZFL on these pages. From the league page, you can navigate to various batting leaderboards and pitching leaderboards. The AFL is accessible from our minor leagues home page.

2 Comments | Posted in Announcement, Baseball-Reference.com, Data

Cuban Stats Added to Baseball-Reference

Posted by Mike Lynch on February 5, 2015

We are happy to announce that we have added Cuban National Series statistics from 1997-98 to 2013-14 thanks to the efforts of Brian Cartwright. First thing's first, though. You should go ahead and gawk at Jose Abreu's Cuban stats. That's right, he hit .453 in 2010 with 1.583 OPS. Those both led the league, but his 33 HR merely tied Yoenis Cespedes for first.

These statistics can be navigated to via our Minor Leagues section here. Once in the minors section, look for Foreign leagues and select Cuban National Series. You can select a season and access batting leaders & pitching leaders from there.

Alternately, if you just want to find Cuban stats for an MLB player like Yasiel Puig, just go to the Minors tab from his player page. Or you can use the search form to go right to the page of a hot prospect like Yoan Moncada. On a player's minor league stats page, the Cuban statistics will show up with the league abbreviation CNS like in the image of Erisbel Arruebarrena's page below.

Cuban Screen Shot

 

We hope you enjoy this new feature. We would also like to note that we will be adding statistics from the current season once is it completed.

5 Comments | Posted in Announcement, Baseball-Reference.com, Data, Features

Explore PFR’s Super Bowl Section

Posted by Mike Lynch on January 23, 2015

If you haven't seen the Super Bowl Section of our site yet, you should head over and check it out right now, because we think it's pretty awesome. Here are some of the features you'll find once you get there:

And best of all is the Super Bowl Play Finder tool. It's similar to the Play Index Game Play Finder tool, but limits your searches strictly to Super Bowls and allows you to search through every play of all 48 previous games. Some examples:

Our Player Game Finder and Team Game Finder are also unique tools for Super Bowl research. You can use them to find things like every 100-yard rusher in Super Bowl history, the largest point spreads in Super Bowl history or the highest over/unders. You can also identify trends such as the record of the team leading after one quarter (26-11), at halftime (36-10) and through three quarters of play (39-8).

So go ahead and try the Super Bowl Section right now -- it's free, easy to use, and best of all, with it you'll be able to dominate anyone who challenges you in Super Bowl trivia.

UPDATE: We have also added a Super Bowl filter to our Drive Finder, which allows users to find things such as the longest drives in any Super Bowl since 1998 or the fastest Super Bowl touchdown drives since 1998.

1 Comment | Posted in Announcement, Data, Features, History, Play Index, Playoffs, Pro-Football-Reference.com, Super Bowl, Uncategorized

2015 Hall of Fame Features

Posted by Mike Lynch on January 6, 2015

With the announcement of the 2015 Baseball Hall of Fame class this afternoon, here are some useful links from around the site:

Please enjoy these features as you debate with your friends today.

13 Comments | Posted in Announcement, Awards, Baseball-Reference.com, Data, Hall of Fame

Browse our Biographical Data

Posted by Mike Lynch on December 22, 2014

The holiday travel season is a time when many of us revisit our roots and return to our hometowns and home states. With that in mind, we thought now would be a good time to remind folks of a data-rich, but perhaps rarely seen portion of our site: Bio Data

This corner of baseball-reference features various totals by place of birth, place of death and place of burial.

For instance, it's probably no surprise that California leads all states with 47,958 home runs (more than 3 times more than any other state). But did you know that the 28 players born in New Mexico have the best cumulative OPS? Or that managers born in Florida are the most games over .500?

You can also compare various statistics across birth countries.

And our most recent addition is the ability to sort by age at time of death. Virgil Trucks, for instance, was the oldest former player to pass in the state of Alabama.

There's a lot of interesting data to play around with in this section. Next time your team hires a manager, perhaps they should look in the United Kingdom and avoid Australia, for instance. And, above all else, never scout for pitching help in North Dakota.

Happy Holidays, from Sports Reference.

Comments Off | Posted in Announcement, Baseball-Reference.com, Data, Features, History

First Downs Added to Team Game Finder

Posted by Mike Lynch on November 26, 2014

We just wanted to quickly note that we have added First Downs (for & against) as a search criteria in the Team Game Finder. Additionally, we have added breakdowns for First Downs by rushing, passing & penalties since 1999 (total First Downs are complete back to 1940). Here's a few examples of these new searches:

These searches are just the tip of the iceberg here and we encourage users to dig in.

2 Comments | Posted in Announcement, Data, Play Index, Pro-Football-Reference.com

Advanced Stats Added to Team Game Finder

Posted by Mike Lynch on November 24, 2014

Users of our Play Index have likely grown accustomed to searching through the Team Game Finder to find things like highest-scoring games or best shooting performances. However, over the years basketball fans (and our users) have grown more statistically savvy and often crave a deeper perspective beyond the raw numbers. For that reason, we have included an advanced box score within our games boxes for some time. Now, we have taken the next step by allowing users to search through these advanced statistics via the Team Game Finder.

To use these tools, you can simply go to the link above and set the parameters you would like for your search. Please note that these advanced stat searches are limited to the era for which we have complete box scores (since 1985-86). Here are some examples:

Please note that cumulative searches utilizing possession-based metrics will differ slightly from some season totals found on team pages and in the team season finder because our box scores have player turnovers, but not team turnovers, which causes slight variations.

Comments Off | Posted in Advanced Stats, Announcement, Basketball-Reference.com, Data, Play Index

2015 Payroll Estimates Added

Posted by Mike Lynch on November 14, 2014

Thanks to Matt Swartz at MLB Trade Rumors, we have 2015 arbitration estimates to flesh out our projected team payrolls for 2015. MLBTR's list can be found at this link. We have incorporated these estimates into our 2015 team payroll estimates, which can be found on table form on our front page (as seen below). The "#" column is for the number of players signed, while "Pyrl" represents the committed payroll on players signed for 2015. Finally, "Est" is an estimate of the team's final payroll for the season:

Screen Shot 2014-11-14 at 11.51.14 AM

 

Any team can be clicked on to find a fuller table with information on individual players. There is also a mouseover for each team showing their most recent payrolls for perspective on their past spending habits.

Comments Off | Posted in Announcement, Baseball-Reference.com, Data

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