The Home Town Free Kick Bias In The AFL

A suggestion that came into my feed on Twitter was that there is a greater "home ground" bias in relation to free kicks at Subiaco than at other grounds. I thought this would be easy enough to investigate - turns out though that there is no handy compilation of free kicks data to be found on the net (at least not that I'm aware of). Nevertheless I was able to compile some free kicks data for last season to see how the "home ground" bias varied across teams. The method I have used is to compare, for each team, the ratio of free kicks for to free kicks against when playing at home against interstate sides with the ratio of free kicks for to free kicks against when playing away against interstate sides. I used this difference to measure the "home ground" bias because some teams are good at picking up free kicks both home and away (see West Coast Eagles).

The results are in the table below. The first thing to note is that teams playing at home against interstate sides were far more successful at getting free kicks than teams playing away against interstate sides in 2011. But in terms of which teams were more successful at getting free kicks at home compared to on the road there doesn't seem to be much of a pattern. Keep in mind these are small samples, particularly for the Victorian teams. But for 2011 at least, it seems that the Subiaco co-tenants were good at picking up free kicks wherever they played.

	Ratio of free kicks for to free kicks against when playing at home against interstate sides (2011)	Ratio of free kicks for to free kicks against when playing away against interstate sides (2011)	Difference
Carl	1.65	0.87	0.77
Haw	1.31	0.72	0.59
NM	1.17	0.65	0.52
Rich	1.18	0.70	0.48
GC	1.18	0.79	0.40
PA	1.35	0.96	0.39
Geel	1.17	0.87	0.30
Adel	1.10	0.84	0.27
Syd	1.09	0.84	0.25
Melb	0.94	0.70	0.24
Fre	1.24	0.99	0.24
Bris	1.08	0.85	0.23
WB	1.21	0.99	0.22
WC	1.29	1.09	0.19
StK	0.91	0.73	0.18
Ess	0.87	0.87	0.00
Coll	1.08	1.26	-0.18
Total	1.16	0.86	0.30