Saturday, April 27, 2013

Avoiding the Drop: To Score Or Not To Be Scored On?

It's almost that time of year again. Clubs at the wrong end of the table are starting to fret; supporters are getting anxious and take to Twitter. Managers' palms - well, of those managers who haven't been sacked - are sweating a little more ... The specter of the drop starts to loom, as the freshness of the early season is but a distant memory, long ago having given way to the reality of not having accumulated enough points.

We have written about relegation before, so this is mostly a quick follow up from our data vault. What seems to matter more, scoring goals or not conceding them? If you're running a football club, where should you have put your money in January, offense or defense?

At first glance, the numbers seem to tell us that they both matter, as the data of goals (scored and conceded) and points in the graph above show. You can win more points by scoring and you'll win more points by not conceding. But curiously, this doesn't necessarily mean they're equally valuable strategies for avoiding relegation.

When we compare the offensive and defensive production of clubs that were relegated with those that weren't, a slightly more interesting picture emerges.

The data show that, over the sixteen seasons between 1995/96 and 2010/11, teams that stayed in the Premier League scored about as many goals as they conceded - 52 v. 47, respectively. In stark contrast, relegated clubs conceded many more goals than they scored - 37 v. 66. You may think this is obvious; and it is. Poor performance means not scoring and being scored on.

But the key is that there is an interesting (and maybe an important) asymmetry: the 37 goals that relegated teams scored, on average, is 71% of the 52 goals non-relegated teams scored - a difference of 29%. But the 66 goals relegated teams conceded are 140% of the 47 non-relegated teams let in - a difference of 40%.

And even if we compare the clubs ranked 18-20 with those ranked 15-17, we see a difference of 10% on offense and 14% on defense.

The numbers are pretty straightforward; on average, clubs that stay in the league score about as much as they concede. Clubs that go down lose the battle against relegation in front of their own goal; defense is their (statistical) Achilles heel.

So when in doubt and seriously worried about the prospect of relegation: spend your money, time, and effort on upgrading your defense. Your supporters may not appreciate the kind of football that produces in the short run, but they'll be happy when they get to see Chelsea, the Manchester clubs, and Arsenal next year rather than Huddersfield, Peterborough, or Burnley.