Tempo-free Primer

I know that some of the stuff that happens on the blog can be a little confusing to people who don’t check out Ken Pomeroy every day (and his blog) or read Basketball Prospectus (you should). I’m establishing this page as a resource so that there is somewhere for readers to get more background on tempo-free statistics and concepts that I use to do my analysis. If you have any questions feel free to email me at john[at]nycbuckets[dot]com or leave a comment on this page.

The Basics:

The game of basketball is broken down into possessions. A possession ends when the ball is given to the opposing team. Of course there are a variety of ways to do this including a rebounded missed shot, a made shot, or a turnover. Obviously the objectives are pretty simple. You want to stop the other team from scoring on their possessions and score during yours. (Hopefully I haven’t revealed anything earth shattering here.)

We can calculate possessions using a simple formula:

Possessions = FGA + .475*FTA + TO – OR

Having the number of possessions tells us a lot about the tempo or pace of the game. Teams like Iona and Long Island want to play very fast, typically more than 70 possessions per game, whereas slow-down defensive teams like St. Peter’s typically fall in the low 60s.

The important thing to note here is that we can now calculate Points Per Possession scored and allowed by dividing points scored or allowed by the number of possessions in the game. A rough threshold for being a good offense or defense is if you’re sitting over (offense) or below (defense) a point per possession.

Now, those things that can happen on a possession to either help score or prevent points? Dean Oliver categorized those as the “Four Factors” in his seminal tempo-free work Basketball On Paper.

The Four Factors:

The four factors are Effective Field Goal Percentage, Turnover Percentage, Offensive Rebound Percentage, Free Throw Rate. Each is relatively simple to calculate.

Effective Field Goal Percentage is essentially field goal percentage with some extra credit for making your three-point shots.

eFG% = (FGM + 3PTFGM * 0.5) / FGA.

Turnover Percentage is how often you turn the ball over on offense or force turnovers on defense. This stat is especially important for teams like Wagner or Manhattan that play a pressing style of defense.

TO% = TO / Possessions.

Offensive Rebound Percentage is how often you grab one of your misses and extend possessions.

OR% = OR / (OR + Opp. DR)

Free Throw Rate is a measure of how often you go to the free throw line.

FTR = FTA / FGA.

While some of those four factors are more important than others, those are the key components of how an offense works. Hopefully now you’ll have a better understanding of those concepts when you read about them on the blog. I’ll continue adding to this as it seems appropriate.

Further reading:

Ken Pomeroy on the Four Factors

The Only Colors’ Tempo-Free Stats for Dummies

Stats Primer on Basketball State (helpful because it’ll show you the best and worst in the nation in many statistics)