Footballing Trends I

Last night I was writing something about the weekend’s seemingly unusual action in the Premier League. There’s no doubt it was pretty unusual, and so I thought I’d flesh out a little more the bits of analysis I did there, here.

The first question was whether goals have become more prevalent now than they were before. Undeniably, there’s been a lot of goals this season in the Premier League — an average of 3.8 when it’s usually 2.6–2.8 per season.

But we’ve only played 38 matches out of the usual 380. So there may well be 38-game stretches with similar numbers of goals? In the left hand plot below, the circle is the most recent 38 matches, and then moving backwards is each previous set of 38 matches by date, rolling through the sample match-by-match, all the way back to 1888.

What it says is that indeed, this is quite unusual — if you take the last 50 years of football, at any rate. The right hand plot is a histogram, or density, which gives some sense of how often 3.8 goals per game happen in a 38 game stretch. The thick green line is 3.8 goals per game.

The black density is over all time, and hence picks up the 1880s, and the 1930s, 1950s and 1960s, to suggest that while it wasn’t super unusual, 91% of 38 game spells had fewer goals per game.

But the red density is for 38 game stretches since January 1 1970, and the thick green line is right in the tail. This most recent 38 games has had the most goals since then. So it’s been pretty unusual.