As I've said a time or two, one way to tell how good a team is is to look at how much of something it does on the pitch. More goals = better. Seems logical, it's not very hard to figure out, and you don't need to know very much about numbers to understand it. Hence, it shouldn't be surprising that counting things up has been the primary way of evaluating quality in football.
But another and perhaps more intriguing way to gauge performance is by looking at how well someone (or several someones) perform a particular task. That's where we get into the business of measuring and evaluating things like individual or team efficiency. Efficiency is a measure of quality, not just quantity.
Assuming most people wouldn't disagree with the idea that players who score more goals on fewer tries are better, I was curious if there are any discernible trends in efficiency across the big leagues of European football. Are leagues getting better (here defined as "more efficient")? Do we see improvements in football efficiency, as we do in many other areas of economic activity, from logistics to how we use energy?
So just for kicks, here's a quick look at goalscoring efficiency across the big leagues measured by the goals to overall shots ratio (measured at the team/match level) in the Bundesliga, the Premiership, La Liga, and Serie A. Below you will find graphic representations of efficiency ratios (goals to shots) averaged across all teams and matches for each season since 2005-06 (the period for which I was able to get data for all four leagues). Guess what?!
The Bundesliga has seen consistent improvement over these six seasons, while shooters in Serie A have gone on a steady decline when it comes to efficiency. By the 2010/11 season, Serie A was clearly the least efficient of the four big leagues. In contrast, the Premier League and La Liga do not show clear trends and instead appear to fluctuate a fairly constant mean. One exception: the 2008/09 Premier League season, in which teams were almost as bad as Serie A has been for a few years now.
So what does this all mean? As a native German who is only too aware of cultural stereotypes (thanks to helpful family members), I did cringe a little bit when I saw the Bundesliga getting more efficient and the Italian league become more profligate. All stereotypes aside, we do have to give the "Most Improved Efficiency Award" to the Bundesliga and the "Most Consistently Efficient Award" to the Premier League.
But more than anything, I was surprised to see Serie A go on such a noticeable decline over such a relatively short period. Of course, it could be that the window of time covered by the data isn't long enough and that the picture would look different with, say, 20 years of data. We don't, so that's speculation at this point. But when you couple these numbers with the leagues' financial health or attendance numbers, you do start to worry about Serie A and you feel good about the trajectory the Bundesliga is on.
