What Lead's a Good Lead in the AFL?

This 2015 season, seven rounds in, has felt like one where leads of any size have been less comfortable.

Maybe that's down to memories of the Swans comeback win over the Dons in Round 1 after they trailed by 34 points at the start of the final term, or the more recent and, perhaps, more dramatic Saints revival against the Dogs in Round 6 as they rallied after trailing by 49 points at the main break (and 54 points part way into the third term).

But, it turns, 2015 hasn't been all that different from 2014 in terms of the importance of different sized leads at each change.

The table below chronicles the eventual fates of teams with variously sized leads at different points in games from the past five seasons. The End of Quarter 1 Summary, for example, provides the win-draw-loss statistics for teams with leads in a given range at the end of Quarter 1. 

On the left is the summary data for the current season where we see, for example, that of the 13 teams that led by 1 to 5 points at the end of the 1st Quarter, 8 eventually won and 5 lost. That's a 62% record. The 70% figure shown next to the 62% provides the winning rate of teams with leads of this size or greater at the end of the 1st Quarter. A little lower down in that same column is a 75% figure, which tells us that three-quarters of teams with leads of 18 points or more at quarter-time, eventually prevailed.

The larger percentages at the foot of each block of the table provide the winning rates for teams with any lead at the end of the respective quarter, treating draws and games where the teams were tied at quarter's end as half wins. This year then, 69% of teams that have led at the first change have gone on to win. That's just 4% less than the figure for the entire 2014 season, including Finals, and identical to the 2013 season figure.

The Quarter 2 statistics suggest that, if anything, 2015 has been a season in which half-time leads have tended to be safer rather than more insecure in that teams with any lead at half-time have won 84% of contests, up from 81% in 2014 and 78% in 2013. Only two of 31 teams with leads of 4 goals or more have gone on to lose in 2015, and only three of 41 teams with a lead of 3 goals or more have suffered the same fate.

Quarter 3 statistics make much the same point about the security of leading. So far this season only seven of the 63 teams that have led at the final change have eventually been run down, and only one of those led by 3 goals or more. Just three teams have lost after leading by a goal or more at three-quarter time.

So, to summarise, leads this season appear to have been no less secure than leads in seasons past, and a team might expect to win at least 90% of the time if it:

  • Leads by 5 goals or more at Quarter time (this is a little different from previous seasons where a lead of 4 goals might have been sufficient)
  • Leads by 3 goals or more at Half time
  • Leads by 1 goal or more at Three-Quarter time