Tanking in the AFL

Most AFL followers believe that ‘tanking’ – teams intentionally losing games, or at least not trying to win them - has occurred in the past, but what is the best way to prove that it happened? Here’s a statistical method that might offer some evidence.

From 1999 to 2006, a team received a priority pick if they had less than 20.5 premiership points (i.e. five wins or less) in the previous season.  This was the largest incentive to ‘tank’, as it gave you an extra high draft pick – at best, the team might not only have the first draft pick but also the second draft pick. Hawthorn’s Lance Franklin and Collingwood’s Scott Pendlebury are examples of players that their teams would not have been able to pick up without this rule. In 2007, the AFL changed the rules so that this incentive was removed; a team could still get a priority pick but it was either in the second round of the draft, or they had to be crappy for two years to get an extra first-round pick.

Hence, one way of finding evidence for tanking is as follows. For each season from 1999 to 2006, we ask: for the last team in the season that disqualified themselves from being able to receive a priority pick (that is, earned over 20 premiership points), how many matches had they played? Then we can compare this to when the last team would have disqualified themselves (that is, earned over 20 premiership points) for each season from 2007 onwards, if the old rule had applied. If tanking occurred, you would expect that the last team in the season to get over 20 premiership points would have done it sooner in the season during the era when the priority pick rule applied. Or in other words, when the priority pick rule applied, teams would hold off on earning more than 20 premiership points for much longer.

The results:

Season	Matches played by last team for season to earn over 20 premiership points
1999	15
2000	18
2001	15
2002	19
2003	19
2004	18
2005	16
2006	19
2007	14
2008	22
2009	21
2010	19
2011	18
2012	22

 

From 1999 to 2006, the average number of matches that the last team that disqualified themselves from the priority pick had played when they earned more than 20 premiership points was 17.4. This included two times when no team disqualified themselves from the priority pick after round 15, which suggests some rather prolonged tanking in those seasons. After the rule was changed, the average number of matches that the last team that disqualified themselves from the priority pick had played when they earned more than 20 premiership points was 19.3. But this number is dragged down considerably by the 2007 season, which may have to some extent been affected by Carlton qualifying for a priority pick under the new rules. Remove this season, and the average is 20.4.

Basically then, there seems to be little to no reluctance to earn more than 20 premiership points for the season now there is no significant disincentive for doing so. Along with the further changes to the rules in 2012, perhaps the removal of this incentive means that tanking allegations are now going to be largely consigned to history.