The Correlation Between Shots Per Game and Goals Scored
Of course there is a correlation between shots taken and goals scored, but what are the factors that influence this relationship?
One of the stranger conclusions of Charles Reep, the first man in Britain to take seriously the collation of football data was that, as teams scored, on average, with one in nine shots, they should shoot more, even if that meant taking almost indiscriminate pot-shots from 40 yards. Even if it didn’t go in, he theorised, a shot might win a corner or a block could create a chance for somebody else.
There is, obviously, a correlation between how many shots a team has and whether it wins any given match - teams who are on top will naturally tend to have more shots - but there remains a huge difference between the chances of a forward scoring if he’s five yards out or forty-five yards out.
This is born out by looking at shots per game this season. It’s no great surprise to see Manchester City (17.7) top - they are, after all, the league’s top scorers with 81 goals.
Chelsea, the champions and the second top-scorers, are fourth (14.7) in the list - a reflection, perhaps, of their more reactive approach in big games. By drawing the opposition on to them and looking to strike on the counter, they play in a way that will yield fewer chances, but those chances are more likely to be one-on-ones than speculative efforts from range or players hurtling onto crosses in packed areas.
Nor is it any great shock to see the likes of Sunderland (10.7), West Brom and Aston Villa (both 10.8) at the bottom of the list. Sunderland struggle so badly with accuracy that their last two goals have come from shots that weren’t on target before taking one or more kindly deflections.
Burnley, the lowest scorers in the division (27), are perhaps higher than might have been expected with the fifteenth highest shots per game (11.5), but their problem has been accuracy - only Aston Villa (3.2) are averaging fewer shots on target per game (3.3).
The big anomaly in the list is Queens Park Rangers, who are averaging the fifth most shots (14) of any side in the Premier League, but are bottom of the league and have scored the fourteenth most goals (41). The quirk is partly explained by a glance at shots on target: of the 14 shots QPR have on average each game, only four have been on target - the 10th highest figure. QPR, in other words, have a lot of shots, but either fewer of them are clear chances, or their forwards lack the precision required in the Premier League.
Charlie Austin is averaging 3.7 shots per game, the second-highest figure in the league behind Sergio Agüero (4.4). He has scored 17 goals and seems likely to get a call-up into the England squad this week, suggesting the policy isn’t a bad one. 1.5 of his shots per game have been on target, which is roughly comparable to Agüero, who has 1.8 shots on target per game.
Of Austin’s efforts, 0.5 have been with his head as opposed to 0.3 of Aguero’s. That’s not a perfect measure, but the greater proportion of headed chances, the more a player is dealing with crosses, which offer a lower likelihood of scoring than shots when the ball is under control.
Austin, then, hasn’t been the problem. The issue has been with the likes of Eduardo Vargas, Niko Kranjcar, Leroy Fer and Matt Phillips, whose goals return has not matched up to the number of shots taken.
Reep, of course, was right to point out a correlation between shots per game and goals per game, but it didn’t take his meticulous stat-taking to realise that. What’s apparent is that the conclusion he drew was far too simplistic: not all shots are equal, and while there is a correlation between shots and winning, it is neither so simple nor so direct as he made out.