Truii data visualization, analysis and management AFL

AFL: Why do you get a point for missing?

From our quick look at the history of Australian Football League games, behinds have very little bearing in the game outcome. This post is to showcase a new public dataset available on Truii – some key game statistics for every game of AFL played (May 1897-May 2014). Go and analyse how your team has performed over the last 127 years.


AFL Scoring

The Australian Football League (AFL) was first established in Melbourne Australia in 1897 as the Victorian Football League. AFL is a very popular sport in Australia, particularly in the country’s south. The game is played on a traditional cricket oval, with each team trying to kick an oblong ball between goal posts. There are four goal posts, if you kick the ball between the centre two posts you score a ‘goal” (6 points). If you get it between the first and second post or 3rd and fourth post you get a single point (or behind). That is, you get six points for a goal, but unlike any other sport I can think of, you also get a point for a near miss. This has always struck me as odd. The complicated scoring system is great for kids to hone their mental arithmetic but I wonder how necessary it really is.

AFL Data

The dataset covers 14,481 games (every game played from May 1897 until May 2014 including finals compiled on this great site: AFL Tables ). An average AFL Game has a team score of 85 made up of 12 Goals and 12 behinds and the average margin is 32 points. In the history of AFL, there have only been 151 tied games (about 1%), thanks largely to the very high scoring nature of the games and the extra point you get for missing helps to sort out the minor differences in most matches.

So what if we didn’t give points for missing?

If there were no behinds in AFL then we would end up with more tied games. In fact, it would have been 940 tied games (6.5%) in the history of AFL (compared to 151 games or 1%), which is still pretty low and could be easily solved by a golden point or extra time approach like other football codes employ.

It is also interesting to consider how often behinds decide a match. That is, how often did the team with the most goals lose the match. To consider how important behinds are, I simply looked across all 14,481 games to determine when the match winner was not reflected in the team that scored the most goals. Or another way, if we changed the record books to remove all the behinds, then in how many games would the winner have changed? The result is surprisingly few – there were a total of 270 games (1.8%) where the winner based on goals alone was different to the winner based on goals plus behinds. So for a given AFL season, having no behinds would have resulted in a different winner in about 4 of the 207 games each season. This seems pretty reasonable to me and is unlikely to have had any real impact on the collective outcomes of the last 115 years of AFL football. It seems we have been doing the complicated mental arithmetic mostly just for fun.

This data set is great for looking at how the game has changed over time. Firstly check Figure 1 to see how the total game points has grown from an average total game score of around 80 points (both teams points combined). Up to a peak of 220 points per game in high scoring 1982. We currently average about 180 points per game. The obvious question is “why are the scores higher?”. Maybe it is because of some subtle rule change to make a free-flowing game, tighter shorts introduced in the 80s or maybe a change to synthetic balls may mean we are kicking further. Or perhaps we are just missing less because those high paid performance coaches actually do something.


Figure 1: Average total game points per year.

So have our sophisticated sports training regimes made us any better at kicking goals? A simple ratio of goals to behinds should increase if we are getting more accurate. Figure 2 does show a clear increase in the goals/behinds ratios. We have improved from a ratio of around 0.65 (about 1.5 behinds for every goal kicked) to 1.16 (about 0.85 behinds for every goal kicked). That’s about an 80% improvement in goal kicking accuracy. This may go some way to explain the dramatic increase in the number of points scored in a game over the last 100 years.


Figure 2: Ratio of goals to behinds for each year (higher score = more accurate)


So let’s put Figures 1 and 2 together (in Figure 3)- it seems that our improvement in accuracy accounts for about 80% of the variance in increasing game score. In Short, match scores are higher because we are more accurate kickers.


Figure 3: Total game score vs kicking accuracy

There is plenty more worth exploring in this great dataset -how has your team’s performance changed through the years? did the franchise expansions have an impact? What is the longest losing spell? The data is available in the sample data library in your Truii account.

The viz’s are easy to make . All you need to do is create a free Truii account to create and publish your own data visualizations.
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