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Larsen/Silliman U.S. Backgammon Ranking
Posted By: Barry Silliman
Date: Tuesday, 11 November 2014, at 12:38 a.m.
In Response To: Larsen/Silliman U.S. Backgammon Ranking (Havard Raddum)
Hi Havard,
The formula for weighted average is actually
weighted_average / (MAX(weighted_events, 10))
That is, if weighted events is less than 10, then 10 is used as the denominator. If you scroll down the list you'll see that this is true for everybody with weighted events less than 10. Dana just happens to jump out at you since he is #2 on the list.
There are actually two "magic numbers" involved in the rating formula with respect to weighted events. 10 is one of them, as I've explained above. The other is 50. The x factor in the second rightmost column is actually
MIN(SQRT(adjusted_weighted_events/50), 1)
where
adjusted_weighted_events = MAX(weighted_events, 10)
therefore x will vary from SQRT(10/50) to 1, that is, 0.447 to 1.000.
These "magic numbers" are built into the formula in order to encourage attendance, which is one of the goals of the rankings. (This is also why more recent years are weighted more heavily than years in the more distant past).
Another goal of the rankings is to provide tournament directors an objective rating that they may use if they wish to aid in establishing eligibility criteria for events.

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