A few days ago David Biderman – of the Wall Street Journal – offered an examination of the history assists in the NBA (see The NBA’s Most Misleading Number). This article led me to think a bit more about assisted baskets and NBA history. And this is not just because I am quoted in the article.
Before I get to what I was quoted saying in this article, let me offer this interpretation of NBA history.
Assisted History
The National Basketball Association – via a merger of the National Basketball League and the Basketball Association of American — came into existence in 1949. If one looks back on that first season – via Basketball-Reference – one is struck by how little data was tracked. The numbers we have to track the productivity of a player from the 1949-50 season consists of points scored, shooting efficiency (from the field and the line), assists, and personal fouls. There is no data on rebounds, turnovers, steals, or blocked shots. So no data was tracked that would allow one to evaluated the impact a player had on gaining or maintaining possession of the ball.
Looking at the available data one wonders (at least I wonder) how it was decided to track these specific numbers. Certainly one suspects – as we think is true today – that scoring dominated player evaluation in 1949. So it’s understandable that people would record data on shooting efficiency and total points. And personal fouls had to be tracked because of the rules of the game.
But why track assists? If I was a reporter I might be inclined to track down someone familiar with the early history of the game. But I am not a reporter (and this is just a blog) so let me just offer some speculation based on simple economics.
Here are four basic propositions about the game of basketball in 1949.
1. Scoring dominates player evaluation. Again, this appears to be true today and given the data tracked in 1949 was likely true 50 years ago.
2. Without the three point line, shots closer to the basket – where shooting efficiencies are higher – are more valuable than shots further from the basket.
3. With a focus on scoring and getting shots closer to the basket, big men who could score inside are going to be valuable (think George Mikan).
4. Big men, though, lack the coordination to advance the ball across the court. In other words, big men need someone to get them the ball. Hence there is a need in basketball for little men or guards.
Guards, though, have an incentive problem. If players are rewarded for scoring, little men have less incentive to pass the ball. But if little men don’t pass the ball to the big men, the team will be less likely to win.
To solve this problem — I would argue — teams started tracking assists. In other words, teams essentially told guards that if they passed the ball to someone who scored, the guards would get rewarded for this behavior.
Now, one should note – especially in the era of the scoring point (see Isiah Thomas or Stephon Marbury, etc…) – guards still have an incentive to focus on scoring. But at least with assists tracked, guards have some incentive to pass the ball.
Assisted Trends
Let’s go back to the Biderman’s article. In this article he poses the following question:
Why are there more assists per field goals made now than 50 years ago?
Here is Biderman’s data:
Until the early 1970s, most teams were awarded assists on about half of the field goals they made in a given game. That number jumped to 60% by the end of that decade and has hovered around that level ever since. (Last season, the average team was given assists on 58.4% of their made field goals.)
David Biderman contacted me about six weeks ago to discuss this trend. As I have noted in the past, interviews with the media are like a test. Except you don’t always know the questions and you don’t get much of a chance to study. So my answer to Biderman’s question was essentially off the top of my head. And here is what Biderman reports I found on the top of my head:
Dave Berri, an associate professor of economics at Southern Utah University and lead author of “Wages of Wins,” a sports analysis book, says the uptick in assists is a function of players improving their shotmaking over the years. He says players in the 1950s and ’60s shot poorly, so more baskets came after offensive rebounds, where no assists are awarded.
It’s certainly true that players in the past shot very poorly. If we look back at the 1949-50 season we see the average field goal percentage was only 0.340. It was not until the 1959-60 season that this average surpassed the 0.400 mark. And it was not until the 1969-70 season that the league surpassed the 0.450 mark. With more missed shots it seems likely that in the 1950s and 1960s a made field goal was more likely to follow an offensive rebound, as opposed to a pass. Consequently fewer made shots had an assist.
To test this idea all we have to do is track how many shots followed an offensive rebound in the 1950s and 1960s. And then we can compare this result to what we see today.
Of course there are some problems with this approach. Offensive rebounds weren’t tracked until 1973-74. And play-by-play data is a very recent innovation. So it looks like we are out of luck.
Although we cannot do this study, I would love to see a different study of assists. Specifically, I would like to see what would happen if the NBA stopped tracking assists altogether. Well, that’s not really what I want. What I want is for the NBA to stop telling players about their assists. I suspect we would see passing in the game diminish. Without the assist in the box score, players should have less incentive to pass and therefore we should see less passing.
Unfortunately, I don’t think I am going to get that study either. I can say that the impact assists have on player evaluation appears minimal. At least, it’s not nearly the impact we see from scoring totals. So although I think assists are tracked to encourage passing, I think the incentive system in the NBA still encourages players to focus on scoring. And in that sense, I don’t think basketball has changed much in 50 years.
– DJ
The WoW Journal Comments Policy
Our research on the NBA was summarized HERE.
The Technical Notes at wagesofwins.com provides substantially more information on the published research behind Wins Produced and Win Score
Wins Produced, Win Score, and PAWSmin are also discussed in the following posts:
Simple Models of Player Performance
What Wins Produced Says and What It Does Not Say
Introducing PAWSmin — and a Defense of Box Score Statistics
Finally, A Guide to Evaluating Models contains useful hints on how to interpret and evaluate statistical models.
Wages of Wins Journal 
David
April 5, 2009
Professor Berri,
What do you think about the concept of the league tracking whether assists lead to free throws or 3 pointers, and would you make adjustments to the way you calculated win score?
dberri
April 5, 2009
David,
Once they collected the data one could look at it. My initial reaction is that I doubt this would make much difference in the measurement of player productivity.
Phil
April 6, 2009
In Elliot Kalb’s “Who’s Better, Who’s Best in Basketball” this is addressed. One of the claims is that until fairly recently, 1980s perhaps, that assists were not rewarded if the scoring player dribbled the ball.
Today, if someone makes an outlet pass to a wide-open player that dribbles once and scores they will be credited with an assist. Usually, they will get an assist even if they player has to contend with a defender. Allegedly, this was not the case 30-odd years ago.
Prof Berri’s explanation makes a lot of sense. But I expect that the subjective way that assists are interpreted, however it may be, plays a role as well. They two are not mutually exclusive, in any case.
JoeM
April 6, 2009
I was watching the highlights of the Mavs game last night. Kidd tied Magic(3rd all-time assists) with a pass to Dirk under the net for a layup.
Then… he passes it to Josh Howard at the top of the key who dribbles 2 times and then takes a jumper and Kidd passed Magic on the list.
mrparker
April 6, 2009
Isn’t the rule of assists two dribbles? I think that there is a conception out there that because assists are rewarded differently then we thought that somehow the ability to accumulate them is overvalued. I contend that the conception is wrong and the fact that a regression based model like wins produced values them goes a long way to prove that point.
Kevin Broom
April 6, 2009
I’ve done a couple mini-studies (5 games in each sample) of the awarding of assists, and in both cases found assist “inflation” (assists awarded when they weren’t (in my opinion) merited), and bias (assists awarded to one player, but not awarded to another in a similar circumstance).
There’s a similar bias issue with the awarding of steals, as well.
brgulker
April 6, 2009
In my view — and this is only anecdotal, from playing and watching basketball — there are only two ways to attribute asissts.
1) Objective. You can establish a rule that says something like an assist is only an assist if one player passes to another and nothing other than that passes occurs between the pass and the made basket — no dribbling, etc.
2) Subjective. And this is how the rules are currently written. This gives some room for flexibility. E.g., if a player makes a steal, passes ahead to a streaking teammate for a breakaway layup — but that teammate had to dribble once or twice in order to not travel. The player who made the steal and pass is ultimately responsible for the score, even if someone else makes the layup/dunk.
Even though the second method is the easiest to exploit and abuse, it makes better sense to me.
The “two dribble” guideline mentioned above would fall under my 1), but even that doesn’t make sense. Did the player make two dribbles in order to avoid a defender (which might negate the assist); or, was the player taking two dribbles on a breakaway layp like I just described above?
Here, the letter of the law is useless because it can’t differentiate between different types of dribbling.
If we can assume that most statisticians are relatively well-trained and that they are (mostly) objective, then I think interpreting assists subjectively makes the most sense.
=======================
I do tend to agree that assists are overvalued in many ways, especially when it comes to individual evaluation.
However, I wonder if they can be of value on a team-wide value. I tried finding the numbers to back this up, but I’m not sure where to look.
My suspicion is that teams who have high offensive efficiency ratings tend to have a higher number of assists per basket than teams with lower efficiency ratings.
I’m more than willing to be proven wrong about this, because it’s mostly an assumption I’ve been making, not necessarily something I’ve backed up with data.
If anyone knows how to look this up, I’d love to test it. I fooled around on basketball reference without much luck…
Joe
April 6, 2009
WHY MUST EVERYTHING HAVE TO DO WITH INCENTIVES. GUYS LIKE MARBURY ARE SCORERS BECAUSE THEIR ABILITY TO SCORE IS BETTER THAN THEIR ABILITY TO PASS. FOR INSTANCE, IVE BEEN A POINT GUARD ALL MY LIFE, AND IVE ALWAYS BEEN A SCORING POINT GUARD. NOT BECAUSE I HAD INCENTIVE TO GAIN POPULARITY OR PRAISE, BUT BECAUSE THAT WAS MY GAME. I WAS A SCORER. THATS WHAT I KNEW HOW TO DO. GETTING GUYS LAYUPS WAS HARDER FOR ME THAN SCORING. ITS ABOUT STYLE OF PLAY. IT HAS NOTHING TO DO WITH INCENTIVES MAN. EXCEPT MAYBE INCENTIVE TO WIN.
Jason E.
April 7, 2009
What is the incentive to leave the caps lock on?
ilikeflowers
April 7, 2009
THANKS JOE! YOUR ALL CAPS OPINION IS VERY CONVINCING! IF YOU HAD JUST ADDED A FEW EXCLAMATION POINTS, I’M SURE DBERRI WOULD REPENT!
ilikeflowers
April 7, 2009
Also Joe, thanks for the anecdotal evidence that the skill of efficiently dishing out assists is more difficult to acquire than the skill of efficiently putting the ball in the basket, and that the incentive to practice this skill requires a greater understanding of the complex concept that easier scoring opportunities lead to more wins. This is clearly beyond the abilities of the capitally-challenged or perhaps it is an indication of the lack of a sufficient drive to win.
‘Sorry I couldn’t do more to help us win fellas. I’m very limited in my skill set and putting in the time to learn something more that will help us to win is too boring, you know practice and all that. You understand fellas…that’s just my game.’
\\ “We’re talking about practice man.”
brgulker
April 7, 2009
pwned
Italian Stallion
April 7, 2009
I suspect that “assisted points” should probably be valued differently than “unassisted points”, but I’m not sure how one would do it.
There’s a kind of chicken and egg situation that exists with regard to great passers (mostly PGs) and great scorers.
If you are a great PG, it has to be a small advantage in terms of accumulating assists to be on a team with superior athletes and shooters.
Superior athletes can catch more passes above the rim and dunk and great shooters will knock down the open shot that results from a great pass a higher percentage of the time.
On the flip side, it has to be an advantage to scorers to have a great PG getting them the ball where they can get higher quality shots.
I think assists, while probably being valued properly in terms of their contribution to wins, are not being valued properly in terms of their value to a team.
When you have a great passer and you lose him, there is usually a huge drop off in skill from that player to his substitute. So the teams loses a high percentage of whatever value great passing adds when the passer is gone.
Great passing is a somewhat limited and unique skill among professional basketball players.
It’s basically the opposite of rebounding, which is probably the most fungible skill in all of basketball.
If you have a superior rebounder and you lose him, the substitute can usually pick up a good percentage of the loss. Some of the slack is also picked up by other teamates on the court. So the net loss to the team is minimal.
Virtually every big man can rebound well if asked to …..well everyone except perhaps Eddy Curry. LOL
Italian Stallion
April 7, 2009
ilikeflowers,
“We’re talking about practice man.”
That’s a big factor, but I doubt it’s that simple.
I think “THE CAPS MAN” is on to something.
It seems to me that when people are in the early stages of developing their skill they often focus their attention on the things they are naturally good at. Success tends to breed further success.
I shoot pool at a fairly high level.
I am much better at 14.1 than Nineball.
To start out, I had a better natural skillset for 14.1 than nineball. That initially caused me to get better results at 14.1, which increased my pleasure playing 14.1, which made me even better at 14.1 etc…
I could improve at Nineball, but I’ll never be as good at it as I am at 14.1.
No doubt a good shooter can become a better passer if he practices (and vice versa), but I suspect some people are naturally better shooters or passers.
vannstruth
April 15, 2009
Interesting that Dave keeps referring to events 50 years ago. Um Dave, 1949 was 60 years ago.