What follows is a guest post from Professor David Berri. You might remember him as the creator of the Wins Produced metric, author of "Wages of Wins" and "Stumbling on Wins," and tenured professor of economics at Southern Utah University. Dave has done extensive work in studying the NBA draft and brings us his overview of this year's draft class. 
 

Update: Below Dr. Berri provided a grade based on the performance we saw. Others try and predict future performance. As Dave notes, this is harder, and even those that do it agree. Regardless, for those looking for a "draft board" Arturo Galletti has put up such a model on his site.

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At the end of every semester in each of my classes, I assign grades.  The choices are A, B, C, D, and F.  Although most of my students pass, a few don't do well and fail (very few!).  Regardless of where the students end up, it is important -- as I often tell students -- to keep grades in perspective.  Yes, there is a tendency for people who do well in school to do well.  But grades are most definitely not destiny. Many "A" students do not end up being particularly successful in life.  And there are many students who do relatively poorly in school that have amazing lives.  

The same basic approach should be taken to evaluating how well NBA draft prospects in 2019 performed in college this past year.  These players took a college class this past season.  In this class, these players were evaluated in terms of shooting efficiency, rebounds, turnovers, steals, etc... (i.e., the factors that primarily create wins in basketball).  With data in hand, the number of wins each player produced per 40 minutes played (Wins Produced per 40 minutes or WP40) was calculated.  And this stat was then used to assign each player a grade in their respective college class.

Again, it is essential to remember that just like a college class, grades do not predict the future perfectly.  Yes, there is a statistical correlation between college performance and NBA performance (i.e., if you play poorly in college, you tend not to be a great NBA player). But college performance is not a crystal ball.  A bad grade could mean a player isn't particularly good.  But it could also mean the player wasn't healthy enough to perform well in class.  Or it could mean the teacher (i.e., the coach) wasn't very good.  Or maybe the player didn't try as hard as they could and with a bit more motivation performance could be much better.

The same story can be told about players who get a good grade.  Yes, maybe this means the player is great.  But it might mean the class they took wasn't particularly hard.  For example, maybe the competition the player faced wasn't very good.  Or maybe physically this player was able to over-power their opponents (something that won't happen in the NBA). 

In sum, if your favorite teams drafts a player with a "bad" grade, that doesn't mean your team drafted a "bad" player.  It probably means there are some issue to address. But it doesn't mean there is no hope.

Likewise, we shouldn't put the "A" players in the Hall-0f-Fame just yet.  Most of these players are not going to be All-Stars.  Most NBA players are not "great," and therefore, most players who are drafted won't be "great" either. So, if you are comparing the players drafted on Thursday night to NBA All-Stars you should expect some people to make fun of you.  At least you shouldn't be surprised when this happens. 

Okay, with all that being said, let's get to the grades.  The scale for the grades was determined by looking at how the players who were drafted out of college from 2009 to 2018 performed their last year in college.  Across this sample of 470 players, the average WP40 was 0.188.  An average player in college will produce 0.100 wins per 40 minutes.  So, an average player drafted out of college was quite a bit better than an average college player. 

Of course, relative to the average player drafted out of college, a player with a 0.188 WP40 was.... well, average.  And if we follow a typical grading scale, an average student is a "C" student.  

We can also use the data from 2009 to 2018 to determine the WP40 necessary to achieve each letter grade.  These ranges (and this is not how I grade in class!) were determined by simply breaking this sample into quintiles.  So the letter "A" goes to players in the top 20%, letter "B" to the next 20%, etc...

• Range for "A" player (top 20% of players): WP40 above 0.245
• Range for "B" player: 0.206 WP40 to 0.244 WP40
• Range for "C" player: 0.169 WP40 to 0.205 WP40
• Range for "D" player: 0.126 WP40 to 0.168 WP40
• Range for "F" player (bottom 20% of players): WP40 below 0.126

Given these ranges, here are the grades each prospect for the 2019 draft received.

Zion Williamson was the top player -- per 40 minutes -- in college basketball this past year. In fact, he is one of the most productive college players this century.  But we must remember that being the best student in class doesn't guarantee that you will be the most successful person in life.  College basketball is not the same as the NBA.  So, it is possible Zion Williamson will not become a Hall-of-Fame player for the New Orleans Pelicans.

A similar story can be told about Ja Morant.  He actually produced more wins than Williamson.  But that does not guarantee Morant will be an NBA All-Star.

As I tell students, "B" means "good." So, there is nothing wrong with being a "B" player (or a "B" student).

Tacko Fall is an interesting "B" player.  Right now he isn't projected by ESPN to be drafted.  But he did produce in college, and he is 7-6.  It will be interesting if any team takes a chance on him.  There is some evidence that being tall in basketball helps. 

Okay, enough of the "good" and "great" player in the class.  Here are all the students who didn't do so well.