Player Efficiency Rating

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The Player Efficiency Rating is freelance writer John Hollinger's all-in-one basketball rating, which boils down all of a player's contributions into one number. Using a detailed formula, Hollinger developed a system that rates every player's statistical performance.

Contents 1 Introduction 2 Guiding Principles of PER 2.1 Inspiration of PER 3 Problems With PER 3.1 Problems with PER Projections 3.2 Reference guide 4 Career PER leaders 5 Calculation 6 Distribution 7 External links

[edit] Introduction

The rating is not intended to be the final word on how a player performs, but is designed to inform the debate. The idea is to come up with an objective measurement of how productively each player is actually playing. There are several factors that are not included in the ratings. The most notable is position defense - the part that does not involve blocked shots and steals. But factors like durability as well as less tangible ones (leadership, for example) are others that can not be rated numerically.

The formula, which Hollinger calls the Player Efficiency Rating (PER), takes into account positive accomplishments, such as field goals, free throws, 3-pointers, assists, rebounds, blocks and steals, and negative ones, such as missed shots, turnovers and personal fouls. The formula adds positive stats and subtracts negative ones through a statistical point value system. The rating for each player is then adjusted to a per-minute basis so that, for example, you can compare subs with starters in frequent playing time debates. It is also adjusted for the team's pace. In the end, one number sums up the players' accomplishments (the statistical ones, anyway) for that season. Hollinger arrives at the point values and adjustments in a fairly complex way, which is one of the topics he relegates to his book.

[edit] Guiding Principles of PER

PER is commonly misconstrued as Hollinger's method for finding the ultimate ranking of a player -- however, this is not the purpose of PER. PER was created by Hollinger to give a snapshot view of how well a player contributes to his team. PER takes the statistics that are available and boils them down in a way that's easy to understand. It interprets the things that are known - made shots, steals, assists, rebounds, blocked shots, free throws, missed shots, turnovers, and fouls in a systematic way that can purpotedly objectively interpret player performance. However, Hollinger admits that there are some holes in the PER formula,

Bear in mind that this rating is not the final, once-and-for-all answer for a player's accomplishments during the season. This is especially true for players such as Bruce Bowen and Trenton Hassell who are defensive specialists but don't get many blocks or steals.

PER cannot take into account such intangible elements as competitive drive, leadership, durability, conditioning, or hustle. Hollinger is seeking for a way to invent a more useful statistical tool for analyzing performance:

What PER can do, however, is summarize a player's statistical accomplishments in a single number. That allows us to unify the disparate data on each player that we try to track in our heads (e.g., Danny Fortson: great rebounder, high-percentage shooter, turnover machine, fouls like crazy, etc.) so that we can move on to evaluating what might be missing from the stats.

Hollinger often uses PER to reflect and evaluate on a player's past and in season performances. In this way, Hollinger uses PER to debate playing time and starting roles. Hollinger also uses PER to make preseason projections.

[edit] Inspiration of PER

The main inspiration for Hollinger in creating PER was the Sabermetric revolution which has transpired through the mid 90's through the work of people like Bill James and Rob Neyer. With the inception of the baseball sabermetric statistic system, people began to rethink methods of statistical analysis. The idea of PER, as was the idea of sabermetrics, is to judge players objectively using complex statictical tools.

[edit] Problems With PER

There are some imperfections when judging players on the PER system. As previously stated the formula cannot quantify such intangible qualities as leadership, durability, etc. The projections also don't include defense beyond blocks, steals and fouls, partly because the league has opted to make this area a void in terms of stats. In this way, invaluable lock down defenders such as Bruce Bowen, who simply shut down their assigned man and either hold them to a low field goal percentage (or prevent them from getting off shots at all), are not well reflected by PER. This is why PER and MVP balloting are not always directly on par. Someday PER may have a greater influence on MVP voting but as illustrated in the tables below, the MVP ballots and PER are somewhat in disagreement. Some experts also argue that PER's neglect of player position defense also weakens the ranking. Their stance is that some positions dictate a higher level of fouls and turnovers and thus some players are at a distinct inherent disadvantage in the rankings.

[edit] Problems with PER Projections

The projections are built by looking at comparable players at the same age and how their stats changed in the following season. For players in most age brackets, this is extremely reliable, but there have been so few players to turn pro out of high school in the past two decades that there is a very small sample to work with. While some players who have come out of highschool have shown a lot of promise in their future years, many have floundered and never quite reached their full potential.

[edit] Reference guide

Hollinger has set up PER so that the league average, every season, is 15.00, which produces sort of a handy reference guide:

*A Year For the Ages:    35.0
*Runaway MVP Candidate:  30.0
*Strong MVP Candidate:   27.5
*Weak MVP Candidate:     25.0
*Bona fide All-Star:     22.5
*Borderline All-Star:    20.0
*Solid 2nd option:       18.0
*3rd Banana:             16.5
*Pretty good player:     15.0
*In the rotation:        13.0
*Scrounging for minutes: 11.0
*Definitely renting:      9.0
*On next plane to Yakima: 5.0

[edit] Career PER leaders

As of the 2005–06 NBA season (Courtesy of Basketball-Reference.com)

Rank    Player                    PER
---------------------------------------
1       Michael Jordan            27.91
2       Shaquille O'Neal*         27.82
3       David Robinson            26.18
4       Wilt Chamberlain          26.16
5       Bob Pettit                25.41
6       Tim Duncan*               25.07
7       Neil Johnston             24.78
8       Charles Barkley           24.63
9       Kareem Abdul-Jabbar       24.58
10      Magic Johnson             24.11
11      Tracy McGrady*            23.96
12      Karl Malone               23.89
13      Kevin Garnett*            23.81
14      Hakeem Olajuwon           23.59
15      Julius Erving             23.58
16      Larry Bird                23.50
17      Dirk Nowitzki*            23.37
18      Oscar Robertson           23.20
19      Kobe Bryant*              23.17
20      Jerry West                22.92
---------------------------------------

* = still active

[edit] Calculation

All calculations begin with what is called unadjusted PER (uPER). The formula is:

Where

• ,
• ,
• .

Once uPER is calculated, it must be adjusted for team pace and normalized to the league to become PER:

This final step takes away the advantage held by players whose teams play a fastbreak style (and therefore have more possessions and more opportunities to do things on offense), and then sets the league average to 15.00.

Also note that it is impossible to calculate PER (at least in the conventional manner described above) for NBA seasons prior to 1978, as the league did not keep track of turnovers before that year.

[edit] Distribution

Hollinger distributes the final PER's in his book, the Pro Basketball Forecast. However, for those needing an in-season PER update, KnickerBlogger.net and ESPN.com Insider (a subscription service) update the PERs, along with Hollinger's other special stats, daily during the season.

[edit] External links

• Alleyoop.com, Hollinger's home site
• An in-depth description of how to calculate PER
• Hollinger's articles at SI
• Basketball-Reference.com, Historical NBA statistical site (includes PER)