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Player Efficiency Rating
The Player Efficiency Rating (PER) is an all encompassing basketball statistic. PER is a rating of a player's per-minute productivity on the court.

PER was developed by John Hollinger as a way to compare the relative worth of any two players. PER is not the ultimate ranking on how well a player performs, but it is a good benchmark. The PER formula 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. These categories are assigned point values and then they are adjusted so all players are judged on as equal a basis as possible. They are adjusted to a per minute of playing time scale and then adjusted by an empirical factor representing a player's team's tempo of play. The actual mathematical formula is very complex and is explained in depth in Hollinger's books. The NBA league average PER is 15. However, PER is not an official NBA statistic, yet it is growing in popularity and is widely used and accepted by expert analysts. PER is also commonly used as a tool for ranking players in fantasy basketball.

Guiding Prinicples of PER
Commonly PER is miscontrued as the ultimate ranking of a player. However, this is not the purpose of PER. PER was created 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 we do know - made shots, steals, assists, rebounds, blocked shots, free throws, missed shots, turnovers, and fouls in a systematic way that can 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. It is a starting point for objective debate. In a world where sports news is dominated by high flying dunks and thunderous blocks, some stats can get lost in the mix. Hollinger is seeking for a way to clear away the media clutter,

"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."

PER is basically a barometer to how complete a player's game may be. Hollinger often uses PER to reflect and evaluate on a player's past and in season performances. In this way, PER can be used to debate playing time and starting roles. Hollinger also uses PER to make preseason projections. These projections are often a source of heated debate.

Inspiration of PER
The main inspiration for Hollinger in creating PER was the Sabermetric revolution which has transpired through the mid 90's. Thanks to the work of people like Bill James and Rob Neyer - professional analysts who tirelessly study the game - the common people don't blindly accept what they're told by coaches and announcers anymore. Many times in proffesional sports, the stats of old just don't tell the whole story of how well a player is actually performing. With the inception of the baseball sabermetric statistic system, people began to rethink what stats are really telling of good player. In baseball it has reverberated to the point that it's actually changed how teams operate, from pitch counts to free agency to actual in game strategy. The idea of PER, as was the idea of sabermetrics, is to judge players objectively. Hollinger is trying to foster this kind of analytical transformation among the basketball community.

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, guys who simply shut down their assigned man, holding them to little scoring, 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 disagreeance. Some experts also argue that PER's negligence of player position, more specifically defensive position, 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.

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. This has unofficially become known as "The Darius Miles Effect". Darius Miles's falloff was so staggering and severe that it has proven to be enough of a millstone that the overall projection for players coming out of highschool foresees a decline in PER over the second and third years in the league. Even though the projection forsees a decline, most experts and Hollinger agree that promising young players like Dwight Howard, Josh Smith and Lebron James will most likely continue to excel. As the sample size for players of this characterization grows, the projections will become more and more accurate.

Player Rankings
PER ratings and PER projections can are useful for ranking players in the real world and also in fantasy sport. Here real world rankings and fantasy rankings can be compared to PER and PER projections. For the meantime PER is a slightly better projector of fantasy rankings as opposed to real world rankings like MVP balloting.