PARS: Frequently Asked Questions

What is PARS, exactly?

PARS is the revival of a rating system developed and maintained by World Pinball Champion Bowen Kerins in the 1990's. It uses the Glicko algorithm, a sophisticated method of interpreting competitive play and determining how accurate player ratings are at any given time. The same algorithm is widely used in the chess community, as well as for many online gaming systems.

The essence of the system is this: When you win, you gain rating points. When you lose, you lose rating points. How many points each player gains or loses depends on the quality of each opponent. If you beat a great player, you stand to gain a lot of points. The more you play, the more accurate everyone's rating becomes.

Why does pinball need a rating system?

PARS fills a niche not addressed by other existing systems, although it's hardly a crowded space in the first place. PARS does not depend solely on tournament results; any matches can be accepted into the system, and indeed, playing more frequently yields the most accurate results for all players.

PARS gives every player an equal opportunity to be rated; it's not designed just for top players. Players can set their own goals and compete as often as they like.

How do players start in the system?

Initially, a player with no games played is given a rating of 1400 and an RD of 250.0. There are some players in the database who have different initial ratings; this happened because those ratings were taken from before September 1999. Match results before September 1999 were not carried over into the new system, but the resulting ratings were.

Whoa, whoa, what are rating and RD?

Rating is the system's "best guess" at the player's skill, relative to other players. RD, or Ratings Deviation, is a measure of how confident that rating is. A low RD indicates that the rating is more likely to be accurate, which results from that player having played a large number of games recently. RD increases over time whenever a player has no rated matches, so a higher RD indicates that the rating is considered less accurate.

Why is RD important?

By indicating how confident each rating is, the system can better assess changes in ratings between different players. The use of RD also ensures that players have to remain active in order to appear in the rankings.

So why is the official ranking sorted by "lower bound"? What does that mean?

"Lower Bound" is a player's rating, minus their RD. This means that players who play more often will have an advantage over less active players, but only if they maintain a high rating throughout their play.

It is more difficult to maintain a high rating and low RD than it is to establish a high rating while remaining relatively inactive. Therefore, the most challenging ranking is by lower bound.

The rating minus the RD is analogous to the statistical concept of a confidence interval (although it's not exactly the same because of the nature of the data - go ask a mathematician).

How do you define an "active" player?

An active player must have an RD of less than 90.0 and must have played at least fifty matches in our database. RD values increase over time, and always decrease when a match is played. If you haven't competed in two years, your RD will reach the maximum of 250.0. A typical player will revert to an RD around 125.0 after about one year.

How much data is in the database for PARS?

We have over 100,000 matches recorded! The most current summary can always be found at the PARS home page. If you have data that you believe would help PARS, please contact us.

Why only count match-play results?

Match-play results are consistent and generally well-known. All match-play results are treated equally by PARS. Using match-play results eliminates any guesswork about the relative importance of a #1 qualifying position, or the number of players at an event. This also allows casual players to compete in PARS at any time by agreeing to have their match results recorded and reported.

How are matches between more than 2 players handled?

Matches between 3 to 6 players are treated as individual heads up matches between every opponent, except in the case of doubles (team) matches, where each player's results are only considered against the opposing team's players. Because this exaggerates the effect of larger groups, the change in each player's rating is reduced to 80% for 3-player matches, 60% for 4-player matches, 50% for 5-player matches, and 40% for 6-player matches.

Will it be easier for a league player to get a high rating?

No. Playing more matches does not necessarily lead to a higher rating; rather, it leads to a more accurate rating. A player in a week-to-week league will have a low RD, indicating greater accuracy in their calculated rating. However, to earn and maintain a high rating with a low RD, a player will have to play solid, consistent, winning pinball against their competition.

What does "historical" mean in the full player listings?

It means that there have been no recorded matches for that player since September 1, 1999, when the original database was last updated by Bowen. Match details prior to September 1, 1999 are not available, but ratings and RD values are carried over as starting values in the new system for players who were in the previous database.

How can I track down a specific player?

Just browse the complete listing of all players in the database, sorted by last name.

What if my information is wrong?

For new players at an event, we mark them as being from the state where the event is held. This isn't always true, but it does help narrow down the identity of a player. Also, if a lastname is missing we might use "MISSING" in combination with the name of their league or event. If your information is wrong, contact us with updates!