WFTDA Adjusts Rankings Calculator to Add Decay Function, Releases Post-Playoffs Rankings

October 7, 2016

The latest WFTDA team rankings were released today, incorporating the results of games played through September 30, 2016, to include all of the Division 1 and 2 WFTDA Playoffs. Team rankings are generated by the WFTDA Rankings Calculator, which uses an algorithm to rank teams based on game scores.

The WFTDA Rankings Committee has adjusted the rankings algorithm to add a Semi-Annual Decay Factor for all games played starting July 1, 2016. The Ranking Points Average is now a weighted average of Total Game Points Earned with newer games contributing more than older games. Both membership and the Rankings Committee expressed concern that games from the previous season contributed as much to a team’s average as games from last month, and this update addresses that concern. Adopting the decay function on July 1 will allow the 2017 International Playoffs seeding to be calculated based on the updated algorithm for a full 12 months.

Games played in the most recent six months of the 12-month ranking window have a Decay Factor of 1.0, and games played in the oldest six months of the 12-month ranking window have a Decay Factor of 0.5. In addition, our Ranking Points Average calculation is transitioning to a weighted average to ensure that teams will not be negatively impacted by season scheduling requirements.

The formula for calculating Total Game Points is:

Total Game Points Earned = Win/Loss Factor x Opponent Strength x Decay Factor x 100

The Decay Factor is also applied to the Game Count used to create the Ranking Point Average:

Weighted Game Count = (# of games played in oldest six months * 0.5) + (# of games played in most recent six months)

Because the Decay Factor is applied to the Game Count, the Ranking Point Average is no longer a strict average, but rather a weighted average:

Ranking Point Average = Sum of Individual Game Points / Weighted Game Count

“Adding a Semi-Annual Decay Factor will help our rankings be more reactive to recent play while not adding too much complexity to the model for leagues who want to ‘follow along at home,’” explained Rankings Committee Strategist Loco Chanel. “Rankings Committee constantly evaluates our model, what kind of tweaks we can make to improve accuracy, and how to ensure that it works for our ever-growing membership. I’m proud that our calculator is vetted and approved by WFTDA membership because it’s very important that our teams have a voice in how their performance is measured.”

For more information, please refer to the updated WFTDA Rankings Policy.

The next rankings will be released shortly after the 2016 International WFTDA Championships, which will be held Nov. 4-6, 2016.

See: Current Rankings

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