Lakers Resurgence: New Team or Regression to the Mean?

By Julian Ryan

The Lakers have risen from the grave. Seemingly destined to hand over their lottery pick to the Suns for much of the season, the team has turned their season around and are now furiously battling it out with the Jazz for the final playoff spot in the West. (Editor’s Note: This article was written before Kobe’s Achilles injury, hence the more optimistic tone — they should still make the playoffs, but their outlook is pretty bleak once they are there without their star player.)

LA started out 17-25 – a far cry from the expected output of the superstar filled team– but have since rallied, going 25-12. Kobe Bryant has rolled back the clock with a series of stellar performances, including a season high 47 points against Portland on Wednesday, earning himself Western Conference Player of the Month in February for his efforts. The turnaround is all the more remarkable given the injuries sustained by starters Metta World Peace and Steve Nash.

Is this improvement in form entirely a result of the team of all-stars finally coming together and clicking as a unit? If the Lakers had objectively improved in the second half of the season, one would expect that their average point differential would be improving. Point differential data can help us strip out some of the luck of winning and losing close games and is thus a good indicator over time of true performance as a complement to simple win-loss percentage.

The graph below charts the Lakers’ winning percentage and point differential over the course of the season. The blue line shows changes in winning percentage by game and corresponds to the y-axis on the right, while the red line shows changes in point differential by game and corresponds to the y-axis on the left.

Screen shot 2013-04-15 at 2.26.30 AM

Looking at the Lakers’ average point differential (+/-) at each point of the season, there does not seem to be a discernible increase during their recent run. Their winning percentage has been increasing while their +/- declines. It appears that to some extent, the Lakers’ luck has turned and they are simply regressing to the mean. They were 3-7 in their first ten games decided by five points or less, and since then have been 9-2 in such fixtures. Their increasing winning percentage is more likely a return to the true quality of the team this year, its perception not distorted by close losses, than an increase in the quality of the team.

All of this does not take away from the achievements of the team. The big three of Bryant, Howard and Gasol have all improved their game and deserve credit for dragging the Lakers back into contention. However, the data would seem to suggest that regression to the mean through better luck in close games may also be at play.

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  • I think you need to clarify the following line? If I understand the graph properly it shows winning percentage by game and point differential by game, not the “changes in” each of those two. That would be an entirely different graph. Thanks for the post, though.

    “The blue line shows changes in winning percentage by game…while the red line shows changes in point differential by game…

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