Defense is Half the Game

I’m fond of criticizing NBA pundits for failing to recognize that defense is half the game into their commentary, but it has occurred to me now and then that this issue perhaps could be studied in a more statistically thorough way. Fortunately, Tyler Cowen recommended the blog of 20 year-old Matthew Rognlie today and it turns out he did some of the math back in February:

Why not just measure the standard deviations of offensive and defensive efficiency in the NBA, and see which turns out to be more important? […] What’s the answer? It turns out that defense really is half the game. In fact, at least in this year’s sample, it’s a little more than half the game, with a standard deviation of 3.39 compared to 3.18 on the offensive side.

It would be interesting to look at this historically and see if there’s a consistent pattern, or a trend that shifts over time, or what. But either way, team defense is hugely important to the game, and the fact that we have a limited ability to quantify it (we have, of course, defensive rebounds, blocks, and steals but there’s more to defense than that) remains the biggest limit to quantifying individual player performance.