What an exciting start to the season. At nearly three goals per game, there have been plenty of great matches. Outlandish score-lines such as 8-2, 1-6 and 3-5 have led commentators to scratch their heads.

The Guardian asks whether it’s money spent on strikers, and Yahoo cites improved attacks and failures at the back. But is the goal glut real?

**Short Term Variation**

The power of statistics is that it accounts for short term variation. When information is limited, we should be wary about drawing conclusions from our observations.

So when we get an “unusual” result, such as 2.98 goals per game so far this season, we can use statistics to tell us if that really is a surprise, or if it’s to be expected – after all, we’ve only seen 99 games.

**How to Predict Goals Scored**

We use our team strength model to predict Premier League matches. Total goals is something we can predict. At the start of the season, for example, we predicted Liverpool to score 1.69 and concede 1.02 goals at home to average Premier League opposition.

So on average, Liverpool home matches will produce 2.71 goals. But that’s only an average – any individual match may produce 3, 4, 5, or even 10 goals. In this example, a “Liverpool V Average PL Team” match has a 22% chance of producing three goals and a 19% chance of producing two goals.

I took our pre-season team ratings and simulated total goals this season 10,000 times. What was the result? We predicted that the 99 matches so far produce 2.82 goals per game on average. That’s may be a surprise in itself – in fact we have consistently predicted the Premier League to produce more than 2.5 goals per game since 06/07. Suddenly 2.98 doesn’t seem such an extreme number of goals.

We can also look at the number of times more than 2.98 goals per game were simulated. The chart shows that it’s not unusual to see 295 or more goals in 99 matches. In fact, 17% of our simulations resulted in 295 or more goals.

In other words, “2.98 goals per match is not statistically significant. We would expect a more extreme result 17% of the time, simply due to natural variation in goal scoring”.

**Trends in Time**

We have been predicting more and more goals in the Premier League since 06/07. The chart shows how many goals we predicted and how many were actually seen. We were surprised about the dip in goals in 08/09 but, apart from that, the predictions and the observations have trended upward.

The final chart shows the the distribution of goals for 06/07 and 11/12. Even though 2.98 goals per game is no great surprise today, it would have been highly surprising – predicted never to happen – in 06/07.

We’d love to hear your feedback – let us know your thoughts in the comments section.

Brilliant post Ian,

I was just about to start a blog post on the same subject,but you’ve totally nailed it.

A great read!

Mark

http://thepowerofgoals.blogspot.com/

What you’re arguing is that the number of goals so far this season is not statistically significantly different to the number you predicted. But you show (at least informally) at the end that the number of goals you predict this season is greater than the number of goals in previous seasons – i.e. you’re saying that there is an increase in the number of goals, albeit one you have predicted.

The articles you mention at the top of the article are asking why there are more goals this season than previously. In light of your data, this seems like a perfectly valid question.

Hi Jim,

Thanks for your comments. I would say the articles I cite are asking what’s special about this season specifically. But there are no more goals than we would expect this season – and there are no more goals than we would have expected at this point last season either.

There is indeed a long term, slow-but-significant trend towards more goals in the Premier League. But that doesn’t tally with a Goal Glut this season.

Whythe goals are increasing is another, more difficult, question. On footy has done some good work trying to answer that:http://onfooty.com/2011/11/goal-glut-in-the-premier-league.html

Excellent post.

Although not perhaps of interest to you, this analysis indicates that us Fantasy Football players should be wary of depending too much on defenders.

So, the point is that for those that have analyzed the trends, the amount of goals should be of no surprise. But would you also say that the “outlandish score-lines” are effects of that long-term trend? Perhaps a product of the widening financial gulf between teams? Or are they simply outliers?