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3-Point Shooting in the NBA: Long-Term Trend or Fad?

Any time you see a process changing, it's important to determine why. Is it indicative of a long term trend, or is it a fad that you can ignore since it will be gone shortly? 

For example, in the 2014 NBA Finals, the San Antonio Spurs beat the two-time defending champion Miami Heat by attempting more 3-pointers (23.6 per game) than any championship team in league history. In the 2015 regular season, the Golden State Warriors made more 3-pointers than any NBA team event attempted from 1980-1988. And this season Steph Curry, by himself, has attempted more 3-pointers than the average NBA team attempted from 1980-1994.

As I said, when you see a process changing, it's important to determine why. Are you seeing a long-term trend, or is it a soon-to-fade fad? If it's the former, you don't want to be left behind as everybody else moves on without you. But if it's the latter, you don't want to waste time and money changing your entire process for something that won't help you in the long run.

Of course, this applies outside the world of sports, too. Whether you're trying to remove defects from your process, determine how the market for your product is changing, or develop the best strategy for your basketball team, it's always good to know all the details on the changes going on around you. So let's see if the increased use of the 3-pointer in the NBA is here to stay, or if it is a fad that might fade away once Steph Curry leaves the league.

The History of the NBA 3-Pointer

The NBA introduced the 3-pointer in the 1979-80 season. At first it was considered a "gimmick" and wasn't heavily used. But as time went on, teams become more and more reliant on the 3-point shot. In fact, the number of 3-point attempts per game has increased from 2.8 in 1980 to 23.7 in 2016!

Time Series Plot

This increase in the 3-point shot isn't some new fad. It's actually been going on since the 3-pointer was introduced to the league! (The bump you see from 1995-97 resulted from the NBA shortening the 3-point line before reverting the line to its original distance in 1998.) Now, with the success Golden State has had in implementing a strategy that emphases 3-point shots, it's likely that other teams will follow suit and increase the number of 3-pointers per game even further in the coming years.

So what is the driving force behind this increase? Well, it's just simple math! Since 1980, teams have pretty consistently made about 48% of their 2-point shots. That means when you shoot a 2-point shot, your expected points are 0.48 * 2 = 0.96. Now, this number is actually a little higher, since it doesn't include times you're fouled shooting a 2-point shot (which happens much more often than being fouled shooting a 3-pointer), and you get to shoot resulting free throws. So let's just call the number of expected points "1" to make the math easy.

If you can expect to score 1 point every time you shoot a 2-pointer, you would need to make at least 33% of your 3-pointers to have the same expected value. So do NBA shooters consistently shoot above 33% on their 3-pointers? I used Minitab Statistical Software to create the following time series plot of the data:

Time Series Plot

We see that it took awhile for NBA players to consistently make more than 33% of their 3-point shots. Coaches were actually correct in not using the 3-pointer too frequently in the 80s and early 90s. But since 1995, the NBA has averaged a percentage that warrants an increased use of the 3-point line. And if you want to explain the reason behind the amazing start that Golden State has been off to this season, look no further than the amount of 3-pointers they attempt and the percentage they make. They average almost 30 attempts per game, and they make a ridiculous 42.4% of their 3-point attempts! You would have to make 63.6% of your 2-pointers to have the same expected number of points as the Warriors' 3-point shots! For some perspective on how hard that is, in his best season, (2013-14) LeBron James made only 62.2% of his 2-point shots.

So 3-point shooting has been steadily increasing from the start, NBA players have consistently made over 33% of their 3-point shots since 1995, and now 3-point shooting has Golden State on track to have the best record in the history of the NBA. Add it all up, and there is only one conclusion:

3-point shooting isn't going away anytime soon.

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