IECG Rating Rules


      |\_       IECG Rating Rules, Version 1.7 May 27th, 1999
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I. General Principles

1. The IECG Rating Scheme is a numerical scheme, in which 
   percentage results can be exchanged into rating differences 
   and rating differences  into percentage performance probabi-
   lities. It is mainly based on the ICCF Rating Scheme.

2. The basis of the scheme is the normal probability distribution.
3. The performance probability is calculated by the formula  
   P(D) = 1/(1+10^(-D/400))

   P(D) is the performance probability  
   D is the difference of the ratings of the two players.
4. The expected rating changes based on the percentage result is 
   given by
   D(p) = -400 * log10((1-p)/p)

   D(p) is the expected rating change  
   p is the percentage result of the player

   and D(0) = -800 and D(1)= 800
5. The formulas used in I.4 and I.5 are good approximation of the
   tables used by the ICCF.
6. The percentage result is calculated by  
    p = (2*W+D)/(2*N)
    p is the percentage result  
    W is the number of wins in the rating period  
    D is the number of draws in the rating period  
    N is the number of finished games in the rating period.
II. Rating Period and Rating Method
1. The Rating Period is 2 months. The first period 
   of a year starts on January 1st.  
2. The Rating List is published on the first weekend of every second month
   on the IECG Webserver at . At the same time
   the representatives from the IECG Tournament Offices receive
   a special version of the rating list.
3. For calculating the ratings, the opponents Tournament Entry Ratings, 
   which are valid on the day of the rating run, are used.
4. Ratings are calculated in batches. A batch is made of all 
   games of a player finished in the rating period. The batches 
   do not necessarily contain all results of a tournament.

5. The Rating List contains the following information:
    a) Position on the list  
    b) Position in the players class  
    c) Players Membership Number  
    d) Players Name  
    e) Players Country  
    f) Players Rating 
    g) Players Tournament Entry Rating (TER) 
    h) No of rated games of the player with the new scheme  
    i) Players Win-Draw-Loss Statistics  
III. Established, Provisional and Starting Ratings, Performance
        Differences of Opponents Ratings.

1. A player has an established rating, if he/she has finished 
   at least 15 games, otherwise his/her rating is called 
2. New players get a starting rating, established by a method 
   explained in section VII. 
3. Provisional ratings are not published until at least six 
   games are accepted for rating.  
4. The Rating Office can publish intermediate ratings on the first
   weekend of the months where no rating is calculated. The published
   Performance is calculated as if the rating period had ended
   on this particular date. However, the tournament entry rating is
5. The performance is not calculated for the first six games, 
   i. e. it is treated as the provisional rating.
6. To determine which Class or Quad Tournament a Player may 
   enter or in which IECG Cup Group a player may start, his/her 
   Tournament Entry Rating is used. The only exception are 
   qualifications according to the corresponding tournament 
7. The Tournament Entry Rating (TER) is equal to the Established 
   Rating in the last published Rating List. For Provisional 
   Ratings, the TER is equal to the Starting Rating, unless at 
   least 10 games are finished.

8. To keep the influence of largely different ratings small for the
   preliminary (and established) ratings, a rating cut-off is used.
   Anytime the difference is larger than 400 points, the opponents
   rating is treated as being 400 points (one tournament class) 
   higher/lower than the players rating.

IV. Calculation, Publishing and Use of the Provisional Rating  
1. The Provisional Rating is calculated by  
   Rp = Rc + D(p)*F  
   Rp    Provisional Rating  
   Rc    Average of the opponents tournament entry ratings  
   D(p)  Expected rating change based on I.4   
   F     A Correction factor given by  
         F = -2*p*p+2*p+0.5
2. The provisional rating is published for the first time after
   six games are finished.

3. (deleted)

4. If at least 15 games are finished, the provisional rating 
   becomes an established rating. This promotion can take place 
   only at the end of a rating period. Any additional games are 
   treated as results for the provisional ratings as well.

V. Calculation of Established Ratings  
1. For each finished game the rating change is calculated by

   dR = k*(W-We) 
   dR    Rating change  
   W     True game result (win 1, draw 1/2)  
   We    Expected result (calculated following V.2.)  
   k     Development coefficient (see V.3.)
2. The expected result We is calculated using I.3. with the 
   rating difference of the two opponents. It is called P(D) in 
   section I.3.
3. The development coefficient is a stabilisation factor and is 
   given by
   k = r*p 
   r = 10           if Ro >= 2400   
   r = 70-Ro/40     if 2000 < Ro < 2400  
   r = 20           if Ro<= 2000
   p = 1            if Pn >=80  
   P = 1.4-Pn/200   if 30 < Pn < 80  
   P = 1.25         if 15 < Pn <= 30  
   P = 1.5          if Pn <= 15

   Ro    is the Rating from the previous rating list  
   Pn    is the number of all rated games upto the previous 
         rating list.  

4. The next rating is calculated by

   Rn = Ro + SUM(dR)


   Rn       new rating of the player  
   Ro       old rating of the player  
   SUM(dR)  Sum of all rating changes as calculated in V.1. 
            for each game.
   This whole paragraph has been taken from the ICCF regulations 
   with only minor changes. 
VI. Sequence of calculation
1. There is no special calculation sequence required, since   
   - all ratings are taken out of the previous list 
   - no unrated players exist in the rating list (see VII)  
VII. New Players
1. New Players with an established ICCF rating will be treated 
   as having an established IECG rating, since the IECG rating 
   calculation is derived from the ICCF system.  
2. New Players with an established rating from a different 
   organization or with a provisional ICCF rating do get this 
   rating as his Starting Rating. If required the national 
   rating will be converted into an FIDE rating with the 
   appropriate conversion rule. No plus or minus points 
   relative to the IECG Rating are used. The established rating
   must be based on at least six games.
3. New players without a rating will get a Starting Rating of 
   800 or a rating estimated by the tutor. This rating should not
   exceed 1700 points.
VIII. Forfeits, Withdrawals, Inactive Players
1. Forfeits based on arbiter decision (claim on time, etc) 
   are rated as normal finished games. This is normally a 
   single event with an individual player.  

2. Withdrawals from tournaments are generally not rated 
   depending on the tournament secretary decision.
3. The remaining players may request an adjudication of the 
   game to gain rating points. The adjudication is binding. 
   Based on the result of the adjudication the rating is 
   updated. However, the game is treated as a win in the 
   score tables.
   Note: This regulation can lead to a loss of rating points 
   of the remaining player, if the adjudication result is 
   not a win, but a draw or even a loss!
4. A player is called inactive, if he/she is not playing a 
   game in a rating period.  
5. Inactive players are removed from the rating list after 
   being inactive for one year. Their rating keeps valid for 
   another four years. Then the player is deleted from the 
6. If an inactive player becomes active, his/her rating from 
   the database is still used.
IX. Transfer regulations from the Old to the New IECG Rating 
    Scheme, Inauguration of the Scheme  
1. All IECG games started before June 1st, 1996 have to be 
   rated with the old scheme, if they are finished before 
   January 1st, 1997.
2. From January 1st, 1997 all ratings are calculated following 
   this document.
3. All games started after August 1st, 1996, have to be cal-
   culated following this document.

4. This scheme comes into operation commencing January 1st for 
   all games after the reorganization. Games finished before 
   this date are treated as being finished afterwards.
5. With the inauguration of this document the following steps 
   are taken:  
   a) All established IECG ratings based on at least 15 games
      are transferred to the new rating scheme as established 
   b) All established IECG ratings based on less than 15 games
      are used as a starting rating. If more than 5 games are finished,
      the opponents average for the provisional rating is calculated
      following IV.1.
   c) All provisional ratings are left unchanged and stay 
      provisional until 15 games are finished.  
   d) All starting ratings are checked if the players does 
      have an ICCF rating. This ICCF rating replaces the 
      IECG rating, if it is higher, and is used as an 
      established rating.
   e) All players who have won an old Class M tournament (#001 to #013)
      before January 1st, 1997 are rewarded an established rating for
      this extraordinary result.

X. Contacts

1. All results must be sent to the corresponding Tournament
2. All questions concerning the table should be send to the
   Rating Official. 
3. The current Rating Official is Dr Ortwin Paetzold  
The IECG Council           

Last updated     :  May 27th, 1999

Update History:

             Date           Description of Changes
Version 1.0  Jan 1st, 1997  First Release of the IECG Rating 
Version 1.1  Mar 3rd, 1997  Section VII.4: addendum to sentence 
                            4 about the correction factor. The 
                            sentence now reads:
                            "The Starting Rating is calcu-
                            lated according to IV.1, but with an 
                            correction factor of F=1."   
                            Section III.3 is disabled until real 
                            automatic routines working with mail 
                            are available
                            Section III.7: The number of games 
                            required for a change of the Starting 
                            Rating is increased to 10, as has been 
                            originally discussed and decided in 
                            the IECG Council Mailing List in 
                            October 1996.
Version 1.2  May 29th, 1997 Section IX.5 changed: part a) added, part
                            b) changed, it read:
                            "All established IECG ratings are used
                            as a starting rating."  
Version 1.3  June 1st, 1997 Section III.7 changed, it read
                            "The Tournament Entry Rating is equal to the 
                            Rating in the last published Rating List, if 
                            more than 10 games are played, otherwise it 
                            is equal to the Starting Rating."
                            The new version explains the use in more detail.
                            Section IV.3 has been deleted, since it is covered
                            by section III.7. 
Version 1.3.1 July 13th, 1997 Correction of the formula in I.6
Version 1.4 December 30th, 1997 Addendum to VII.4, added the sentence with the 
                            Starting Rating boundaries.
                            Deletion of R Steinkellners Web-Server URL in II.3
Version 1.5 April 5th, 1998 Section III.8 added to keep top players with preliminary
			    ratings playing in the Cup.
			    Section IX.5.b) extended by the last sentence.
			    Section IX.5.e) added.
Version 1.6 September 27th, 1998 Comment on Discontinuation of Rating Tournaments.
Version 1.7 May 27th, 1999  Adaptation of the Rules to current Practice (length of 
                            Rating Period, Format of Rating List, Webserver etc.)

Last modified on Thursday, May 27, 1999

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