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Adding Box Plus/Minus (BPM) to College Basketball

Posted by David Corby on February 11, 2015

Just a note that we have added Box Plus/Minus (BPM) to our College Basketball site this week.

As outlined in its introduction to Basketball Reference, BPM is an advanced stat intended to measure a player's total contribution as reflected by advanced, context-dependent box-score metrics like USG% and AST%. It was developed for the NBA using regression techniques against a 14-year-long sample of historical Regularized Adjusted Plus-Minus (RAPM) data. BPM estimates the number of points contributed by a player greater or less than an average player, per 100 team possessions.

We're able to calculate BPM for seasons dating back to 2010-11 and it can be found initially on player pages in the 'Advanced' table, on our school season pages, also in the 'Advanced' table, and we've also added several advanced stats - including PER, Win Shares, and BPM - to the conference registers, along the right side of that page. (see below image). However, the best way to view BPM, as a sorted leaderboard, or according to any other criteria - is to use our Play Index search tools.

 

bpm_cbb

 

Again, our thanks to the creator of BPM, Daniel Myers, and to those whose work serves as a component. The methodology and logic of Box Plus/Minus (BPM) is discussed in our About section, and please note the section specifically for the NCAA.

 

(Note that the 'Advanced' tables on the player and schools pages have changed just a little, to accommodate the new stats. Individual ORtg and DRtg have been moved to the 'Per 100 Possessions' tables and Points Produced - the main component of ORtg - has been moved further to the left on the 'Advanced' table.)

 

* We have published BPM but not VORP for college basketball, unlike the NBA.  Value over Replacement Player (VORP) owes its meaning and derivation to a market with salaried players and teams on an equal footing, and thus an easy-to-establish theoretical "replacement level", which doesn't exist or make sense for the NCAA.

 

Comments Off | Posted in Advanced Stats, Announcement, Basketball-Reference.com, CBB at Sports Reference

Sports Reference Welcomes Adam Wodon to Our Staff

Posted by sean on February 9, 2015

Adam Wodon has joined Sports Reference today as a Managing Director for Hockey Reference. Adam will be working out of our Philadelphia office as our staff size has now risen to six. Adam brings a great deal of development experience and hockey knowledge to Sports Reference. Adam is the founder and managing editor of College Hockey News. Adam is an Isles fan through and through and also supports the Mets, Jets, and Nets making him the first diehard National League fan on staff. Adam is also on twitter at (@chn_AdamWodon).

Hans VanSlooten (@CantPitch) who had been working on the hockey site for the last 14 months will be taking over primary day-to-day development of Baseball-Reference.com.

2 Comments | Posted in Announcement, Baseball-Reference.com, Basketball-Reference.com, CBB at Sports Reference, CFB at Sports Reference, Expire30d, Hockey-Reference.com, Olympics at S-R, Pro-Football-Reference.com

Box Plus Minus/VORP for the Playoffs

Posted by David Corby on February 9, 2015

 

Playoff Box Plus/Minus (BPM)

We're now able to calculate Box Plus/Minus (BPM) and Value Over Replacement Player (VORP) for the playoffs, by extending the methodology used for the regular season, and calculating a team efficiency rating based on performance in the playoffs, adjusted for strength of playoff lineups (by using playoffs minute distributions and regular season BPM ratings). These ratings are interesting in themselves, and reflect some of the great playoffs runs - the 1996 Bulls' rating was +19.3, and the 2001 Lakers were +20.1.

The BPM figures themselves reflect the best individual playoff performances. LeBron's 2009 BPM of 18.2 is tops by a large margin, followed by Kareem's 1977 run and then the Jordan playoffs from 1989-1991.

(For a detailed explanation and further discussion see the "Playoff Box Plus/Minus and VORP" section of the write-up.)

 

Playoff VORP (and Pro-Rating the Regular Season)

As well as BPM, we can now calculate VORP for the playoff season. (If you need a refresher on VORP as a concept, please visit the original write-up when we introduced it to Basketball Reference). We calculate VORP for the playoffs similarly to the regular season - that is, [BPM - (-2.0)] * (% of minutes played) - and it should be interpreted identically. Again, that's as the number of points the player has produced over a replacement player, per 100 team possessions.  The significance of VORP compared to BPM is that it's accumulative, rather than a rate stat, and thus accounts more literally for value provided, weighted as it is by minutes played, and expressed on a per-82 game basis*.

(* - Yes, this is new. We are now pro-rating VORP based on the number of games that a team has played during the regular season, and doing the same for the playoffs. One point of VORP is one point of full season team efficiency differential. This affects partial seasons, strike-shortened seasons, and the playoffs.  This has significance for the playoffs, in particular - players on teams that go further or play in 7-game series will accumulate more because they have more opportunities.)

 

Some Minor Changes to the Equation

Please note that we've also updated the methodology, such that some players will have a slight variation in the BPM and associated stats. These were technical fixes to the regression methodology, which had the result of slightly changing the relative value of component stats. For example, blocks and shooting efficiency are two factors that are more highly favored by the revision and thus Anthony Davis saw the largest increase in BPM (+0.8), however most changes were of a much smaller magnitude. Please see the details of this revision in the write-up, under the "Updates" section.

 

Again, Basketball Reference extends its thanks to Daniel Myers, whose research the above represents. Also, please see the revised 'About BPM' write-up that details the methodology and is generally extremely useful for understanding the context of BPM and VORP, and the best ways to think about and use these stats.

 

 

 

2 Comments | Posted in Advanced Stats, Announcement, Basketball-Reference.com, CBB at Sports Reference, Playoffs

Using our Search Engine

Posted by David Corby on January 23, 2015

When we revamped our search engine last year we didn't provide much instruction. After all, it's pretty simple to use. It's fast, features auto-complete, and has nicely categorized search results.

Since then, we've added some new features that should make finding what you want even easier. The following is a quick guide to the most useful tips and tricks.

First thing is first, the search bar is at the top right of the site, and also on the left-hand side of the homepage, shown here, respectively:

 

searchbar2

 

search4

 

Player Search

We match against the player's common name or a known nickname: 'lebron' will return LeBron James; searching 'sir charles' will return Charles Barkley.

Partial strings work, too. For example, 'kentav' will return Kentavious Caldwell-Pope, if you want to save yourself some typing and the player's name is unique.

 

Team Names

Searching for team indexes and seasons is just as easy. 'spurs' will return all Spurs teams since they adopted that name for the 1974 ABA season.

 

spurs_results

 

Clicking on the right column - 'Team Seasons' - will give you a list of individual Spurs seasons, which bring you conveniently to a season summary page.

 

Team Seasons

In fact, there's an even easier way to get to a team's season page. Just add a year before or after the team name.

For example, '1996 bulls' or 'bulls 1996' will bring you directly to that champion Bulls season.

 

League Seasons

What if you want to get to a particular NBA season page to view historical standings, stats, and leaders?

Same trick as for teams, except use the league name: 'nba 1998' or '1998 nba'. This will land you on the 1998 NBA season summary. This pattern works for the ABA and BAA seasons, as well.

 

Playoffs

Likewise, to access historical playoff pages do the same thing, except substitute the word 'playoffs'.

'playoffs 1990' or '1990 playoffs' will send you to the 1990 Playoffs summary page, with links to series stats, leaders, etc.

 

Finals

Finals summaries work the same way.

'finals 1984' or '1984 finals' will give you all the Bird & Magic stats from that year's Finals.

1984finals

 

et cetera

We get a lot of searches that don't fit a particular pattern - for example, mis-spellings like 'dwayne wade', or searches like 'hall of fame'.

Often, these will give you what you're looking for and the best way to find out is trial and error. In fact, 'dwayne wade' will go to Wade's page and 'hall of fame' will land you on our Hall of Fame summary page.

Likewise, 'mj' will bring you to Jordan's page, 'sixers' to the 76ers franchise summary, and 'salaries' will direct you to our database of player salaries.

 

If a common search is missing or there's a term or search pattern you'd like us to add here, please ask!

 

 

1 Comment | Posted in Announcement, Basketball-Reference.com, CBB at Sports Reference

Small Additions to the Player Season Finder

Posted by David Corby on January 6, 2015

Just a note that we've added 3-Point Attempt Rate (3PAr) and Free Throw Attempt Rate (FTr) to our Player Season Finder.

In addition, we've expanded the group of shooting stats that we show by default, now including both eFG% and TS%.

This should help you keep tabs on Kyle Korver's historic sharpshooting...

 

psl_new_stats2

 

 

Comments Off | Posted in Advanced Stats, Announcement, Basketball-Reference.com, CBB at Sports Reference

Draft Stashes List and Stats

Posted by David Corby on December 17, 2014

If you've poked around our Draft section recently, you might have a noticed a new link for 'Draft Rights'. We've compiled a list of all held draft rights for players that are currently playing abroad.

The easiest way to view this is to mouse over the 'draft' item in the navigation bar and look for the link:

draft_stash_link

 

The selections are sorted by the retaining team, then by the year of selection. We have current year stats for all players that participate in one of the Liga ACB (Spain), LNB Pro A (France), Lega Serie A (Italy), or Greek Basket League, as well as the Euroleague or Eurocup. In these cases, the Current Team column will link to those team's pages and you can view the player's season stats there.

draft_stash_page2

 

Finally, if that's not enough, on our team pages we've included the current year stats for all players whose draft rights are retained by that team. In some cases, the player will play in a league for which we don't have stats or might not currently be under contract with a team, but most players whose rights are currently held are active and playing in Europe...

draft_rights_team

 

 

1 Comment | Posted in Announcement, Basketball-Reference.com, CBB at Sports Reference, Draft

Player Season Finder Improvements, Including BPM & VORP

Posted by David Corby on November 13, 2014

Just a note that we've expanded the searchable options in our Player Season Finder this week.

In particular, we've added BPM and VORP to the list of searchable stats, both of which are available going back to the 1973-74 season.  If you don't know what those stats are, you may have missed this recent announcement. Also feel free to weigh in at the discussion on the APBRmetrics forum.

Also, we've added search options by a player's birth state, college, and debut seasons, either in the NBA or ABA. There's also a new option to search by award winners so you can see all seasons by MVP winners, All-NBA selections, Defensive Players of the Year, etc.

If you're new to the site, the Player Season Finder is our most popular database search tool. You can get to it by clicking on 'play-index' in the top navigation menu, then the large 'Player Season Finder' link. It allows you to search for and compare player stats for a season or a player's career (or a span of years). You can also find the number of seasons that match your criteria. As an example, you can find the highest USG% seasons of all timemost career VORP for a player from Duke, or the most points scored in a single postseason.

The new fields are highlighted in red below:

 

psl_new

2 Comments | Posted in Advanced Stats, Announcement, Basketball-Reference.com, CBB at Sports Reference

Introducing Box Plus/Minus (BPM)

Posted by David Corby on October 29, 2014

We're excited to introduce our newest statistical feature, Box Plus/Minus (BPM), developed and shared by Daniel Myers, well known as an administrator of the APBRmetrics forum and the developer of Advanced Statistical Plus/Minus (ASPM), which has performed very well empirically and to which BPM now serves as successor.

BPM is an advanced stat intended to measure a player's total contribution, calculated using box-score data that's available going back to the 1973-74 season. It follows on work done toward the Statistical Plus/Minus (SPM) concept, and ASPM, and uses long-term data sets developed by Jeremias Engelmann, the creator of ESPN's Real Plus/Minus statistic. Please visit Daniel's write-up to read more about the development of BPM, the background of the concept, and everyone that's contributed to the research.

BPM is presented intuitively, representing points per 100 possessions for which the player was on the court. For example, a player with a +4.3 BPM is said to have contributed 4.3 more points than an average player over 100 possessions, based on measurable statistical output from game box scores. The calculation makes heavy use of context dependent box score stats like USG%, TS%, STL% and others (as well as the statistical interactions between these components). We publish these as Advanced Box Score Stats and you can read about these component calculations in our glossary. Note that there is a separate calculation for the offensive component of a player's BPM, which yields both OBPM (Offensive Box Plus/Minus) and DBPM (Defensive Box Plus/Minus).

Further, BPM is scaled so that -2.0 represents a theoretical "replacement level" - thus, this concept is easily extended to permit calculations of one player's value over that theoretical threshold - that formula is [BPM - (-2.0)] * (% of minutes played), which is VORP, and interpreted as per 100 team possessions.

We'll be presenting BPM, it's offensive and defensive components, as well as VORP in the 'Advanced' table of our player pages, and likewise in our team pages:

 

james_harden2

 

For 2014, the leaderboards for BPM, OBPM, and DBPM, respectively, look like the following (> 1,000 MP):

bpm1 opm1 dpm1

And as the season gets underway, you'll be able to find BPM and its components, as well as VORP, on our actual leaderboard as well as other site features like the Play Index tools and season registers.

 

3 Comments | Posted in Announcement, Basketball-Reference.com, CBB at Sports Reference

New Hall of Fame Prediction Model

Posted by David Corby on October 23, 2014

We maintained a Hall of Fame prediction model that, overall, works pretty well. This looks like a good list, yes?

hof

 

However, keep scrolling and you'll see that a few players are slipping through the cracks. Miller is already in and good money is on both Mutombo's and Nash's eventual inductions.

nashmutom

 

 

So we've tweaked our model a little bit. It's no less simple than what we've been doing, but it casts a wider net around those factors that voters and the media prioritize for player inductions. Its criteria include All-Star games, leaderboard appearances, peak dominance, championships, and the player's height (yes, height!). Many of these variables are considered as well by our old model.

A necessary disclaimer is that Hall voters, to varying extents over the years, have used criteria that are difficult to account for in a simple predictive model such as college stardom, FIBA success, foreign careers, and so on. In a nutshell, we're considering plaudits earned while playing in the NBA so adjust as you wish those careers of players like Manu Ginobili and Pau Gasol who have racked up FIBA medals in addition to their pro career.

Anyway, here's the list of the top 25 retired and active players...

 

RETIRED:                                                             ACTIVE:

hof2_car hof2_act

Except for Mutombo (6.4% to 86.8%) nothing changes too dramatically. Ben Wallace gets back in the race, and Nash becomes a virtual lock. Chauncey Billups and Shawn Marion move up significantly while Carmelo falls 10+ points.

To gauge your thinking about how many players "should" get in, here are the number of players in every NBA season between 1979-80 and 1999-00, inclusive, that were eventually enshrined:

active_num

We used the logistic regression method (same as before) and found that this works fairly well:

my $logit = -0.20303
              + -0.14203 * height_inches
              +  0.80573  * championships
              +  0.01594  * leaderboard_points
              +  0.41568  * peak_ws
              +  1.02443  * all_star_games

I'll get the documentation page up shortly which will explain a few of the nuances, for example how we determine "leaderboard points" and a few other particulars.

5 Comments | Posted in Announcement, Basketball-Reference.com, CBB at Sports Reference

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