The EFF stat stands for Effectiveness not Efficiency..
You should be sorry because it stands for Efficiency. 
Go to the Game Stats Live and hold your cursor over EFF%. 
http://www.news.com.au/heraldsun/sport/afl/gameday/0,,5015496,00.html
No you are wrong (and I am sorry correcting grammer got me kicked off one forum) but EFF stands for Effective.
Check the AFL site, check the herald-sun (the hard copy paper), check the dictionary.
Effective - producing a decided, decisive, or desired effect
Efficient - producing an effect, product, etc. with a minimum of effort, expense, or waste
This is the HTML source code from the Herald-Sun. It is "Efficiency".
<th scope="col"><abbr title="Efficiency %">EFF%</abbr></th>
And they actually are using the 'efficient' meaning in their stats. Efficiency percentage - how efficient is a player's disposal. What percentage of their disposal do they not waste.
Become a maths lover '65. It's rigorous, consistent and logical unlike the English language lol .
Just means some programmer some where got it wrong.
Check the actual paper (the hardcopy pieces of paper). The legend at the botoom says EFF - Effective
