Correlation between shot-share and goal-share

Here’s a graph showing every team’s regular season performance at even-strength (5v5) from the 2007/08 season to the 2015/16 season (Source: Corsica Hockey). Getting a higher proportion of the total goals scored for and against is the key to winning games, so that’s displayed in the vertical axis. On the horizontal axis is the team’s share of all shot attempts (i.e., Corsi). Each dot represents every single team by season since 2007/08, with the lockout-shortened 2012/13 season excluded since each team only played 40 games. Comparing a 40-game season to an 82-game season might give us unreliable results (team’s can get hot or cold over a shortened length) so I left that season out and compared apples to apples.

goal-and-shot-share-2007-2016

The black bars that cut through the graph horizontally and vertically mark the average across all the teams over the eight seasons. Not surprisingly, it’s right at 50.01% for both goal-share and shot-share. I’ve also added a trend line, which has a r-squared value of 0.32. It’s obviously not a perfect correlation between shot-share and goal-share, but you increase your chances of scoring if you’re outshooting your opponents. Teams that posted a higher than average shot-share but didn’t see their goal-share get higher than 50% (bottom right quadrant) often had external factors at play. It could’ve been injuries to key players or a lower than normal shooting or save percentage. On the flip side, team’s might have a lower than average shot share, but still outscore oppoenents (top left quadrant). This would be due to a higher than normal shooting percentage (shooters get hot) or team save percentage (goalie gets hot). Hockey is weird like that.

Highlighted in the graph are eight orange dots with a black ring around it. These are the Oilers eight seasons, and not surprisingly they’re all in the bottom left quadrant where you don’t want to be. They’ve been terrible at outshooting opponents, and as expected, they haven’t been able to get a higher share of the total goals except for that one time in 2008/09. They had one of the worst shot-shares in the league that season (46.35%), but thanks in large part to a slightly higher than normal shooting percentage, and some great goaltending from Roloson (a 92.45 save percentage), the Oilers managed to get 50.9% of the total goals.

This season the Oilers would be in the top right quadrant, as they’re getting 52.00% of the total shot attempts, which has them 9th in the league, and are also getting 52.88% of the total goals (i.e., goal-share). Generating shots is a repeatable skill and is dependent on the coaching staff’s on-ice tactics and the skill of the players. A team’s ability to generate shots very often remains consistent through a season, and season-to-season, as long as the coaching staff remains and players stay healthy. The Oilers have a good thing going with their ability to out-shoot opponents, but this in no way guaranetees goals. A lot has to happen for a shot to become a goal, and goalies can always go on hot and cold stretches. But as long as they keep their share of shot attempts up, they’re putting themselves in a position to succeed.

One thought on “Correlation between shot-share and goal-share

  1. Pingback: Eberle and Hall and Stats and Meaning | The SuperFan

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