How does the NPL rating system work?
This basic system was developed by Bob Jewett. Here is his description.
The main advantages of this system over other systems now in use are:
- No individual match score sheets are required. The only results needed for the system are each player’s win/loss record. Not even the game count is needed.
- All tournament results contribute to the ratings. Performances in large-prize-fund tournaments are given extra weight in calculating averages.
- It’s not possible for a player to win a tournament without a rating increase. If a player consistently wins more than 50% of his matches, his rating will constantly increase.
- The adjustment method is simple enough that players can understand exactly why they go up or down and by how much.
- The charts relating ratings to games per match are relatively simple, since only the difference in the ratings of the two players is important.
- All the ratings adjustments are automatic and according to written rules rather than by arbitrary and unexplained decisions.
How does the NPL Handicapped Nine Ball System work?
Each player has a rating; better players have higher ratings. Beginners will have ratings around 20, while professional players will have ratings round 100 or higher. Matches are handicapped by requiring the better player to win more games to win the match. The size of the handicap is determined by the difference between the ratings of the players according to the tables below. For example, if a player rated at 55 played someone rated at 25, the difference would be 30 rating points and the regular match length would be six games to three.
The ratings are adjusted after each tournament. For each match a player wins or loses, his rating goes up or down one point. New players are adjusted faster than that, moving three rating points per match for their first ten matches and then two for twenty matches.
Short Match Regular Match Long Match
(Chart-8) (Chart-10) (Chart-12)
Rating Match Rating Match Rating Match
Diff. Games Diff. Games Diff. Games
0-6 4-4 0-5 5-5 0-4 6-6
7-18 4-3 6-14 5-4 5-11 6-5
19-29 5-3 15-21 6-4 12-17 7-5
30-39 4-2 22-28 5-3 18-22 6-4
40-48 5-2 29-36 6-3 23-28 7-4
49-UP 6-2 37-46 7-3 29-35 8-4
47-56 6-2 36-42 7-3
57-UP 7-2 43-48 8-3
49-58 9-3
59-68 8-2
69-UP 9-2
If the better player is giving up half or more of the match, he has choice on the first break, otherwise lag for first break.
Tables for other length matches are available and may be used.
Optional rules to reduce delay from slow players:
- Speedup Rule 1: If both players have ratings under 45, use Chart-8, otherwise use Chart-10.
- Speedup Rule 2: If the whole tournament is waiting on one match that hasn’t started yet, that match will use Chart-8 instead of Chart-10. Use of this rule is at the tournament director’s discretion.
What is a better way to estimate ratings for new players?
The type of drills called “Progressive Practice” allows a quick, accurate way to measure the basic pool-playing ability of someone you haven’t seen play before.
Read over the explanation of the drills, and try the four drills in Set 1 (1A to 1D) to see how they work. If you get a score of better than 4 on all the drills on one page, go to the next higher set.
When testing someones ability before a tournament, don’t explain the whole system — just enough to let them know exactly what has to be done on each shot. Try to start them at a level (1 through 5) that will be appropriate for their ability. If you are unsure of where to start them, begin with the draw shot in Set 2 (shot 2C).
Keep track of the current position with a coin. If they seem to do a shot easily, increase the difficulty a diamond at a time until they miss, then change the adjustment to half a diamond in either direction for a miss or make. Have them shoot a total of 7 times at each drill, or 28 shots for a whole page. If they manage to get a score of 4 or more on every drill, have them do the next harder page, if there’s time, since the first page was too easy. If they fail to get even one on any single test, try the next easier level of test.
Add up the final positions on the four drills in the set, and multiply by the number of the set to get the total basic ability. For example, if they do set 2, and get scores of 4.5, 4, 2.5, 4, the sum is 15 and the score is 2 x 15 = 30.
Use the following table to translate the “total basic ability” (TBA) into an NPL rating. The example player above would have a initial rating of 58.
TBA Rating TBA Rating TBA Rating TBA Rating
5 20 21 48 37 66 53 84
6 22 22 49 38 67 54 85
7 24 23 50 39 68 55 86
8 26 24 51 40 69 56 87
9 28 25 52 41 70 57 88
10 30 26 53 42 71 58 89
11 32 27 54 43 72 59 90
12 34 28 56 44 74 60 92
13 37 29 57 45 75 61 93
14 39 30 58 46 76 62 94
15 41 31 59 47 77 63 95
16 42 32 60 48 78 64 96
17 43 33 61 49 79 65 97
18 44 34 62 50 80 66 98
19 45 35 63 51 81 67 99
20 46 36 64 52 82 68 100
How do you determine match handicaps from rating differences?
Fair rating differences for various match lengths. For example, a match of 5-3 is fair for a rating difference of 24.1 points.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
1 0.0
2 38.1 0.0
3 58.3 20.1 0.0
4 72.1 33.9 13.7 0.0
5 82.5 44.3 24.1 10.4 0.0
6 90.9 52.7 32.5 18.8 8.4 0.0
7 97.9 59.7 39.5 25.8 15.4 7.0 0.0
8 104.0 65.7 45.6 31.9 21.5 13.1 6.0 0.0
9 109.3 71.0 50.9 37.2 26.8 18.4 11.3 5.3 0.0
10 114.0 75.8 55.6 41.9 31.5 23.1 16.1 10.0 4.7 0.0
11 118.3 80.0 59.9 46.2 35.7 27.4 20.3 14.3 9.0 4.3 0.0
12 122.2 83.9 63.8 50.0 39.6 31.2 24.2 18.2 12.9 8.1 3.9 0.0
13 125.7 87.5 67.3 53.6 43.2 34.8 27.8 21.7 16.4 11.7 7.4 3.6 0.0
14 129.0 90.8 70.6 56.9 46.5 38.1 31.1 25.0 19.7 15.0 10.7 6.8 3.3 0.0
15 132.1 93.8 73.7 59.9 49.5 41.1 34.1 28.1 22.8 18.0 13.8 9.9 6.3 3.1 0.0
16 134.9 96.7 76.5 62.8 52.4 44.0 37.0 30.9 25.6 20.9 16.6 12.8 9.2 5.9 2.9 0.0
17 137.6 99.3 79.2 65.5 55.1 46.7 39.6 33.6 28.3 23.6 19.3 15.4 11.9 8.6 5.5 2.7 0.0
18 140.1 101.9 81.7 68.0 57.6 49.2 42.2 36.1 30.8 26.1 21.8 18.0 14.4 11.1 8.1 5.2 2.5 0.0
19 142.5 104.3 84.1 70.4 60.0 51.6 44.5 38.5 33.2 28.5 24.2 20.3 16.8 13.5 10.4 7.6 4.9 2.4 0.0
20 144.8 106.5 86.4 72.6 62.2 53.8 46.8 40.8 35.5 30.7 26.5 22.6 19.0 15.8 12.7 9.8 7.2 4.6 2.3 0.0
How do you adjust ratings based on different factors?
Rating adjustment rate vs. total matches played in system:
Players new to the system are adjusted faster than the veterans. The amount of adjustment for each match is given by the formula:
Adjustment = Seniority Factor x Entry Fee Factor
Adjust up for each win and down for each loss.
Seniority Factor:
3 for first 10 matches
2 for up through 30 matches
1 after 30 matches
Any match over two years old is not counted towards seniority.
Entry Fee Factor:
1 for up to $20 entry
2 for up to $40 entry
3 for up to $90 entry
4 for up to $140 entry
5 for $150 and up
For example, if someone new (with only 3 matches in the system) enters a big tournament (for $150), they would be adjusted up at the rate of 3×5 = 15 rating points for each match they won. The adjustment should be applied during the tournament (after each match) for players with fewer than 30 matches in the system.
As another example, suppose a veteran with 50 matches wins second in the local weekly tournament with a small entry fee, with a total record of 5-1. That’s 4 net wins, so the total adjustment would be 4 x 1 x 1 = up 4. The adjustment does not depend on the initial rating, only on seniority and size of the entry fee, and of course net wins/losses.
How to match game counts determined from rating differences?
Chart-6
Rat. Match
Diff. Games
0-10 3-3
11-27 3-2
28-UP 4-2
Chart-7
Rat. Match
Diff. Games
0-6 3-3
7-16 4-3
17-27 3-2
28-39 4-2
40-UP 5-2
Chart-8
Rat. Match
Diff. Games
0-6 4-4
7-18 4-3
19-29 5-3
30-39 4-2
40-48 5-2
49-UP 6-2
Chart-9
Rat. Match
Diff. Games
0-5 4-4
6-12 5-4
13-18 4-3
19-28 5-3
29-38 6-3
39-48 5-2
49-56 6-2
57-UP 7-2
Chart-10
Rat. Match
Diff. Games
0-5 5-5
6-14 5-4
15-21 6-4
22-28 5-3
29-36 6-3
37-46 7-3
47-56 6-2
57-62 7-2
63-UP 8-2
Chart-11
Rat. Match
Diff. Games
0-4 5-5
5-9 6-5
10-14 5-4
15-22 6-4
23-29 7-4
30-36 6-3
37-42 7-3
43-52 8-3
53-62 7-2
63-68 8-2
69-UP 9-2
Chart-12
Rat. Match
Diff. Games
0-4 6-6
5-11 6-5
12-17 7-5
18-22 6-4
23-28 7-4
29-35 8-4
36-42 7-3
43-48 8-3
49-58 9-3
59-68 8-2
69-73 9-2
74-UP 10-2
Chart-13
Rat. Match
Diff. Games
0-3 6-6
4-7 7-6
8-11 6-5
12-18 7-5
19-23 8-5
24-28 7-4
29-34 8-4
35-41 9-4
42-48 8-3
49-53 9-3
54-63 10-3
64-73 9-2
74-77 10-2
78-UP 11-2
Chart-14
Rat. Match
Diff. Games
0-3 7-7
4-10 7-6
11-14 8-6
15-18 7-5
19-24 8-5
25-29 9-5
30-34 8-4
35-39 9-4
40-46 10-4
47-53 9-3
54-57 10-3
58-67 11-3
68-77 10-2
78-81 11-2
82-UP 12-2
Chart-15
Rat. Match
Diff. Games
0-3 7-7
4-6 8-7
7-10 7-6
11-15 8-6
16-19 9-6
20-24 8-5
25-29 9-5
30-34 10-5
35-39 9-4
40-44 10-4
45-50 11-4
51-57 10-3
58-61 11-3
62-71 12-3
72-81 11-2
82-85 12-2
86-UP 13-2
Chart-16
Rat. Match
Diff. Games
0-3 8-8
4-8 8-7
9-12 9-7
13-15 8-6
16-20 9-6
21-24 10-6
25-29 9-5
30-33 10-5
34-38 11-5
39-44 10-4
45-48 11-4
49-54 12-4
55-61 11-3
62-65 12-3
66-75 13-3
76-85 12-2
86-89 13-2
90-UP 14-2
Chart-17
Rat. Match
Diff. Games
0-2 8-8
3-5 9-8
6-8 8-7
9-13 9-7
14-17 10-7
18-20 9-6
21-25 10-6
26-29 11-6
30-33 10-5
34-37 11-5
38-42 12-5
43-48 11-4
49-51 12-4
52-58 13-4
59-65 12-3
66-68 13-3
69-79 14-3
80-89 13-2
90-92 14-2
93-UP 15-2
Chart-18
Rat. Match
Diff. Games
0-2 9-9
3-7 9-8
8-10 10-8
11-13 9-7
14-18 10-7
19-21 11-7
22-25 10-6
26-29 11-6
30-33 12-6
34-37 11-5
38-41 12-5
42-46 13-5
47-51 12-4
52-55 13-4
56-62 14-4
63-68 13-3
69-72 14-3
73-82 15-3
83-92 14-2
93-95 15-2
96-UP 16-2
Chart-19
Rat. Match
Diff. Games
0-2 9-9
3-5 10-9
6-7 9-8
8-12 10-8
13-15 11-8
16-18 10-7
19-22 11-7
23-25 12-7
26-29 11-6
30-33 12-6
34-37 13-6
38-41 12-5
42-44 13-5
45-50 14-5
51-55 13-4
56-58 14-4
59-65 15-4
66-72 14-3
73-75 15-3
76-85 16-3
86-95 15-2
96-98 16-2
99-UP 17-2
Chart-20
Rat. Match
Diff. Games
0-2 10-10
3-6 10-9
7-9 11-9
10-12 10-8
13-16 11-8
17-19 12-8
20-22 11-7
23-26 12-7
27-29 13-7
30-33 12-6
34-36 13-6
37-40 14-6
41-44 13-5
45-48 14-5
49-53 15-5
54-58 14-4
59-61 15-4
62-68 16-4
69-75 15-3
76-77 16-3
78-87 17-3
88-98 16-2
99-100 17-2
101-UP 18-2
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