Boxrec Ranking System for those who need to know?

Boxing Record Archive (BoxRec.com) provides "Active" and "All" boxer ratings, as calculated daily by its computer. The "All" ratings include both "inactive" (retired) and "Active" boxers. The "Active" ratings include only those boxers who have had a bout within the past 365 days. (After a year of not fighting, a boxer is automatically designated "inactive" by the BoxRec computer. A boxer is also designated "inactive," or "complete," if he has announced his retirement, even if he may have had a bout within the past 365 days.) Every boxer in the database is rated--even those with an 0-1 record.

These ratings are not influenced by subjective views or opinions, but are wholly dependent upon the bouts contained in the BoxRec server database. The BoxRec computer re-calculates the ratings at approximately 9:35 GMT every day. As the computer refreshes its calculations, a boxer may earn or lose ratings points with every bout he has fought since the last calculation--provided, of course, that a BoxRec Editor has entered that bout into the database before the recalculation. A boxer may also earn or lose points if bouts are added to any of his opponents' records, or to their opponents' records--even if the boxer himself has not had a fight since the last BoxRec computer calculation.

There admittedly are inaccuracies and anomalies, especially in the All-Time ratings, because of incomplete records in the BoxRec database. Although a boxer’s own record may be complete, his opponents’ records may not be complete. Pre-World War II boxers in particular are at somewhat of a disadvantage, vis-à-vis modern boxers. Their opponents’ records often are quite incomplete--because of the scarcity of source material or Editors' time--while the records of opponents of more current boxers often are quite complete. So, for example, while the records of Mike Tyson’s opponents may be quite complete--thereby earning Tyson a certain number of points and giving him a high ranking among the All-Time Heavyweights--the records of Young Stribling’s opponents may be extremely lacking, thereby giving Stribling fewer points and a much-lower All-Time rating. And it may appear to the casual BoxRec visitor that Stribling had fought many boxers making their professional debuts or having had only a handful of career bouts, when the truth is that not all of his opponents’ total career bouts have been entered yet into the database by an Editor. (Too many of those old-time bouts are forever lost in history because they were not reported by a newspaper or similar source, or the source was later destroyed.) But as the BoxRec Editors continue to research older resources and enter “new” historical bouts into the database, the rating of an old-time boxer like Stribling will gradually move up or down, even if his own record is complete--if bouts are added to his opponents’ records, or to his opponents' opponents' records, and so forth. So the BoxRec ratings are continually improving as new bouts are entered into the database. (Presently, some 2,000 current and old-time bouts are entered each week by the BoxRec Editors.)

Further, because of the very few women presently boxing professionally, with some weight divisions having only a handful of active female boxers, a woman with an 0-1 record will appear “world ranked” by BoxRec. This is simply an anomaly due to the few female entries in the database.

Ratings structure

All these ratings evaluate every day all bouts in the database in chronological sequence. A higher rated boxer should be expected to defeat a lower rated boxer with increasing probability by increasing rating difference.
Current ("Active") rating
Every boxer gets a first rating of 0 before his first bout.
After every bout, the ratings of the two boxers involved are changed depending on the bout's official result (KO, TKO, RTD, UD, PTS, NWS, MD, SD, DQ, TD, DRAW).
The value of a result varies between v=1 and v=0.
The clear decision factor varies between cd=1 and cd=0.
The winner cannot lose points for KO, TKO, RTD, DQ, TD and decisions on points with cd=1
KO, TKO, RTD are rewarded with full value v=1, cd=1.
NWS is rewarded with full value v=1 for 12 rounds boxed and more and a lower value related to the number of rounds boxed. Clear decision factor cd=1.
UD, PTS are rewarded with full value v=1 for 12 rounds boxed and more and a lower value related to the number of rounds boxed, clear decision factor cd=1. This is valid, if the score cards are not available.
DRAW is rewarded with full value v=1 for 12 rounds boxed and more and a lower value related to the number of rounds boxed. Clear decision factor cd=0.
MD, SD, DQ, TD are rewarded with full value v=1 for 12 rounds boxed and more and a lower value related to the number of rounds boxed. Clear decision factor cd=0.5. This is valid, if the score cards are not available.
If the score cards are available, the value rewarded is in direct proportion to the rounds boxed, with full value v=1 for 12 rounds boxed and more. The clear decision factor is in proportion to rounds boxed and the mean score difference per judge. cd=1 for a mean score difference per judge of 50% of the rounds boxed.
All bouts are regarded to have the same weight independent of titles.
The winner gets a certain part of the opponent's points and a certain part of the rating difference to the opponent's rating.
For a DRAW the rating of the higher rated boxer is reduced by some part of the point difference; the rating of the lower rated boxer is enhanced by the same amount of points.
The full relative point reward is 33%. It is in direct proportion to the pre-bout rating of the defeated opponent.
The winner can get up to 25 additional points per opponent's launch state rank
The maximum launch state rank regarded is 15 - and so the maximum number of additional points is 375
The maximum additional points are reduced to the opponent's rating but to not less than 6 * (launch state rank +1)
This value is multiplied by the maximum additional points reduced by the own rating, and it is set in direct proportion to the rounds boxed and the clearness of the decision
This value is multiplied by the quotient of the maximum of the opponent rating and 6 * (launch state rank +1) on one side and the sum of the maxima of the opponent rating and 6 * (launch state rank +1) and the maxima of the own rating and 6 * (launch state rank +1
Launch states are:
0 = no recent win
1 = 1 recent win, 2 = 2 recent wins, 3 = 3 recent wins
4 = recent win over opponent with state 3, 5 = 2 recent wins over opponent with state 3, 6 = 3 recent wins over opponent with state 3
7 = recent win over opponent with state 6, 8 = 2 recent wins over opponent with state 6, 9 = 3 recent wins over opponent with state 6
10 = recent win over opponent with state 9, 8 = 2 recent wins over opponent with state 9, 9 = 3 recent wins over opponent with state 9
13 = recent win over opponent with state 12, 14 = 2 recent wins over opponent with state 12, 15 = 3 recent wins over opponent with state 12
The ratings are decreased for moving up to higher weight divisions by the square of the reciprocal ratio of the weights limits of the divisions--and they are increased by the same factor for moving down the divisions.
The rating of a boxer is reduced by 0% to 50%, if he didn't box an opponent with a rating of at least 50% to 0% of his own rating points within 18 months.
The rating of a boxer is reduced by 50% for every time period of inactivity of 18 months.
The pre-bout rating of a boxer successfully returning from inactivity is set to the lower value of his own rating before inactivity and the higher value of his own rating after inactivity and the pre-bout rating of his opponent.
The pre-bout rating of a successfully debuting boxer is set to 25% of his opponents pre-bout rating.


Formula

If a boxer with a rating of r_a before the fight defeats a boxer b with a rating of r_b before the fight with result of value v and clear decision factor cd, the new ratings r_a_new and r_b_new after a fight are, earn_f is 33.3%:
earn = earn_f * v * (r_b*cd + (r_b-r_a)/(1+2*cd));
r_a_new = r_a + earn
r_b_new = r_b - earn

Additional points (no additional loss points accounted):
opponent in launch state n: v * cd * (25*n - r_a) * min( (max(6*(n+1),r_b), 25*n) / 25*n * max(r_a,6*(n+1)) / (max(r_a,6*(n+1) + max(r_b,6*(n+1))


Examples

Boxer a KO boxer b, a has 1000 points, b has 500 points. launch state 4, v=1, cd=1,
earn= 0.33 * 1 * (500*1 + (500-1000)/(1+2*1)) = 111
r_a_new = 1000 + 111 = 1111
r_b_new = 500 - 111 = 389


Boxer a UD 6 boxer b, scores 59:55 58:56 58:56, a has 1000 points, b has 500 points.
A 6 rounder is rewarded with value 6/12, v=0.5
UD is rewarded with cd=1 at maximum
mean score difference per judge is (4+2+2)/3 = 2.667, which is rewarded in direct proportion to half the rounds boxed with cd= 2.667/3 = 0.89 at maximum
so cd=0.89
earn= 0.33 * 0.5 * (500*0.89 + (500-1000)/(1+2*0.89)) = 44
r_a_new = 1000 + 44 = 1044
r_b_new = 500 - 44 = 456


Boxer a SD 4 boxer b, scores 39:37 39:37 37:39, a has 1000 points, b has 500 points
A 4 rounder is rewarded with 4/12, v=0.333
SD is rewarded with cd=0.5 at maximum
mean score difference per judge is (2+2-2)/3 = 0.667, which is rewarded in direct proportion to half the rounds boxed 0.667/2 at maximum\
so cd=0.333
earn= 0.33 * 0.33 * (500*0.33 + (500-1000)/(1+2*0.33)) = -15
r_a_new = 1000 - 15 = 985
r_b_new = 500 + 15 = 515


More complex - Boxer a KO 4 boxer b, a has 30 points, b has 40 points, boxer b is in launch state 3, v=1, cd=1
earn= 0.33 * 1 * (40*1 + (40-30)/(1+2*1)) = 14
r_a_new = 30 + 14 = 44
r_b_new = 40 - 19 = 21
additional points:
1 * 1 * (75 - 30) * min( max(40,4*6), 75) / 75 = 1 * 35 * 40 / 75 = 19
19 * max(30,4*6) / ((max(40,4*6)*max(30,4*6)) = 19 * 30 / (40+30) = 19 * 0.43 = 8
r_a_new = 44 + 8 = 52
All Time ("Inactive") Ratings

The All Time Rating for a boxer is the sum of 33% of the sum of annual rank points he gets for his annual ratings - and 33% of the sum of annual rank points of best defeated opponents - and 14% of his career top rating:
the annual rating is the rating at the end of every year the boxer was active
annual rank points = 200 / annual rank in division cluster
the value of 200 annual points for the top boxer is reduced, if the annual rating of #10 in the division cluster is less than 100 for men, - and if the annual rating of #5 in the division cluster is less than 50 for women
Bout Star Ratings

All bouts are rated with 0 to 5 stars.

Men
5 stars = both opponents have 331 ratings points at least ~ best 100 boxers
4 stars = both opponents have 188 ratings points at least ~ best 300 boxers
3 stars = both opponents have 83 ratings points at least ~ best 900 boxers
2 stars = both opponents have 24 ratings points at least ~ best 2700 boxers
1 stars = both opponents have 1 rating point at least = rated boxers
0 stars = one opponents has not even 1 rating point at least = not rated boxers

Women
5 stars = both opponents have 42 ratings points at least ~ best 30 boxers
4 stars = both opponents have 28 ratings points at least ~ best 60 boxers
3 stars = both opponents have 14 ratings points at least ~ best 120 boxers
2 stars = both opponents have 4 ratings points at least ~ best 240 boxers
1 stars = both opponents have 1 rating point at least = rated boxers
0 stars = one opponents has not even 1 rating point at least = not rated boxers

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