Thursday, February 12, 2015

Are freethrows game-changers?

"And another missed free throw!"
"That's the story of the game right there, they just can't get those easy points from the charity line."

I've heard very similar discussions to this one over and over throughout the years from basketball commentators. Although not truly meaning it (at least I think), the commentator was heavily implying that the outcome of the game would be extremely different if a given team had made all, or significantly more, of its free throws.

Don't expect a sophisticated analysis here, I was just curious to explore the correlation between difference in final score and number of missed free throws.

So I wanted to investigate the two following questions:
  1. If the losing team had made all its attempted free throws, would the outcome of the game have been different?
  2. If the losing team AND the winning team had made all of their attempted free throws, would the outcome of the game have been different?

To answer those questions, I pulled all boxscores for regular season games from the 1999-2000 season to the last complete one, 2013-2014 and for each game tracked the final score difference, as well as the number of missed free throws for both the winning and losing teams.

Here's a first quick visual of the relationship between the number of missed free throws for each team (losing team on the lefthand graph, winning team on the righthand graph) and the final score difference:

Rather surprisingly, there does not appear to be any link between the number of missed free throws and the outcome of the came in terms of close game or huge blowout. It would have seemed natural to assume that the more free throws the loser team has, the more likely they are of getting blown out, and the opposite argument for the winning team.

How have these numbers evolved over time? Here's the evolution of the average score difference and missed free throws for those 15 seasons:

Not completely obvious trends emerge from the graph, but if anything can somewhat notice that:

  • the lines for the winning and losing team are extremely similar
  • average score difference has stayed flat or perhaps very slightly increased
  • number of missed free throws has decreased (could be due to better shooting and/or less free throws attempted, and it's actually a little of both)

Now of course this analysis has been as naive as they come. You can't just expect free throws to go from missed to made and expect the entire game to follow its original course. Players might get confidence as they rack up easy points, and coaches might change strategies if what would have been a big lead is only a 2/3 point lead. The point of the exercise here was to compare the range of final point differential to number of missed free throws, and it would seem that free throws only account for about half the final gap. This could be a reason why teams, coaches, players don't put in crazy efforts to have all players shoot 99%. Their time is probably better spent on other types of training.

That being said, I just had to mention the other day's game which saw both teams shoot a combined 37% (16 for 43, 8 for 25 for the Clippers, 8 for 18 for the Nets) from the free throw line. To put things in perspective, Shaquille O'Neal who was criticized his entire career for those shots was 53% over his career (despite finding elaborate strategies to boost the percentage). Consider the Clippers lost by a mere two points 100-102, I'm sure they must be kicking themselves for their performance at the line.

Also worth noting, this game from 1999 between Portland and the Lakers. Portland won quite big - by 15 - but missed only one free throw. The Lakers missed 17! Had both teams been perfect, the Lakers could have actually won a game they lost by 15. This was the biggest outcome reversal I observed in the data if both teams had been perfect.

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