DATA from independent assessors has said AFL field umpires have made accurate decisions nearly 94 per cent of the time this season as football operations boss Greg Swann says they have worked through early "teething problems". 

The League confirmed its umpiring assessment numbers had shown that 'whistle blown accuracy' from the field umpires was at 93.8 per cent correct this season. 

However that number drops to 89.7 per cent accuracy for the support free kick accuracy – which references when the non-controlling umpire makes a call.

The League would like that number higher, but recognises that support free kicks are generally more difficult and less obvious decisions. 

"From a coaching point of view, to pay a support free kick you have to be 100 per cent sure. It's lower than the normal 93 per cent, so that's being coached and the support free kick is something we have to look at. You don't pay it if you're not 100 per cent right," Swann told AFL.com.au.  

"I'm still happy to be getting nine out of 10 right, because otherwise you miss those support free kicks altogether."

The data is collected from independent callers who sit in the AFL's review centre during games and call and code each decision that the umpires make in a game. The umpires' coaches then feed back the assessments each week to the umpires themselves. 

The data showed that boundary umpires have operated at a decisional accuracy of 98.7 per cent correct this season, with 31 "avoidable errors" this season. This accounts to an error every five-and-a-half games, with the ARC called on around three to four times a round for their assistance on boundary line decisions. 

Under the goal umpiring numbers, there has been 9291 scoring involvements this season with 7932 scoring decisions. Decisions account for every goal and behind through the season and involvements refers to every other decision such as potential scores and marks as well as near goal-line decisions. 

The AFL's data said the goal umpires have recorded four scoring errors this season – three attributed to the goal umpire and one to the ARC – amounting to a goal umpire decisional accuracy of 99.43 per cent according to the data. 

There has been a strong external focus on umpiring this season, but Swann said the data collected reflected the standard of this season. The AFL's best group of umpires will soon step up for the finals series, with its squad of 42 umpires being whittled down to the best 20 for September. 

"There's an independent piece to this, they are watching the game and noting all the free kicks that are paid and that group says they think that's right, wrong or a query, and then they confirm those," he said. 

UMPIRE DECISION DATA

Field umpiring

Whistle blown per game – 40.39
Whistle blown accuracy – 93.8 per cent
Support free kick per game – 6.64
Support free kick accuracy – 89.7 per cent

Boundary umpiring

Decisional accuracy - 98.73 per cent
ARC assists - 71
Boundary umpire avoidable errors - 31
Error rate - 1 error in every 5.52 games
At standard throw ins - 97.54 per cent

Goal umpires/ARC

Scoring involvements - 9291
Scoring decisions - 7932 
ARC overturns - 48
Scoring errors - 4 (ARC 1, Goal 3)
Goal umpire decisional accuracy - 99.43 per cent
Goal umpire + ARC accuracy - 99.96 per cent