It's draft season, when every team is a contender and every fan hopes (and prays) that their team makes the right pick. But if you're a fan of a team with a lottery pick, how optimistic should you be? How much is that fifth overall pick really worth? By looking at data from past drafts we can get an estimate of how much each pick is worth, and once we have those expected values we can answer any number of interesting questions.

I started by looking at all drafts from 1977 through 1991. Why those drafts? Because 1977 was the first post-merger draft and 1991 was the last draft for which there are no longer any active players (Shaquille O'Neal was drafted in 1992). In order to get an estimate of the value of each pick we first have to determine what value is. To me, value is winning games, and I have a statistic named Win Shares that provides a player's estimated contribution to his team in wins. My goal was to come up with an expected career value (i.e., expected career Win Shares) for each of the top sixty picks in the draft. Using statistical techniques, I came up with the following formula:

EV = 76.9 - 18.8 * log(pick)

For example, the expected value of the fifth pick in the draft is:

EV = 76.9 - 18.8 * log(5) = 46.6

On average we would expect the fifth pick in the draft to produce about 46.6 Win Shares. Let's take a closer look at all of the fifth overall selections from 1977 through 1991:

+------+------------------+-------+
| Year | Player           | WS    |
+------+------------------+-------+
| 1977 | Walter Davis     |  78.8 | 
| 1978 | Purvis Short     |  51.4 | 
| 1979 | Sidney Moncrief  |  89.0 | 
| 1980 | James Ray        |  -0.3 | 
| 1981 | Danny Vranes     |  15.0 | 
| 1982 | LaSalle Thompson |  35.3 | 
| 1983 | Sidney Green     |  17.5 | 
| 1984 | Charles Barkley  | 176.0 | 
| 1985 | Jon Koncak       |  28.7 | 
| 1986 | Kenny Walker     |  17.9 | 
| 1987 | Scottie Pippen   | 122.6 | 
| 1988 | Mitch Richmond   |  81.4 | 
| 1989 | J.R. Reid        |  22.5 | 
| 1990 | Kendall Gill     |  48.5 | 
| 1991 | Steve Smith      |  81.7 | 
+------+------------------+-------+

As you can see, eight of these players exceeded their EV while seven fell short.

Here is the value chart for all of the draft picks:

+------+------+
| Pick | EV   |
+------+------+
|    1 | 76.9 | 
|    2 | 63.9 | 
|    3 | 56.2 | 
|    4 | 50.8 | 
|    5 | 46.6 | 
|    6 | 43.2 | 
|    7 | 40.3 | 
|    8 | 37.8 | 
|    9 | 35.6 | 
|   10 | 33.6 | 
|   11 | 31.8 | 
|   12 | 30.2 | 
|   13 | 28.7 | 
|   14 | 27.3 | 
|   15 | 26.0 | 
|   16 | 24.8 | 
|   17 | 23.6 | 
|   18 | 22.6 | 
|   19 | 21.5 | 
|   20 | 20.6 | 
|   21 | 19.7 | 
|   22 | 18.8 | 
|   23 | 18.0 | 
|   24 | 17.2 | 
|   25 | 16.4 | 
|   26 | 15.6 | 
|   27 | 14.9 | 
|   28 | 14.3 | 
|   29 | 13.6 | 
|   30 | 13.0 | 
|   31 | 12.3 | 
|   32 | 11.7 | 
|   33 | 11.2 | 
|   34 | 10.6 | 
|   35 | 10.1 | 
|   36 |  9.5 | 
|   37 |  9.0 | 
|   38 |  8.5 | 
|   39 |  8.0 | 
|   40 |  7.5 | 
|   41 |  7.1 | 
|   42 |  6.6 | 
|   43 |  6.2 | 
|   44 |  5.8 | 
|   45 |  5.3 | 
|   46 |  4.9 | 
|   47 |  4.5 | 
|   48 |  4.1 | 
|   49 |  3.7 | 
|   50 |  3.4 | 
|   51 |  3.0 | 
|   52 |  2.6 | 
|   53 |  2.3 | 
|   54 |  1.9 | 
|   55 |  1.6 | 
|   56 |  1.2 | 
|   57 |  0.9 | 
|   58 |  0.6 | 
|   59 |  0.2 | 
|   60 | -0.1 | 
+------+------+

This method takes the player's entire career into account, but perhaps we should only look at the player's first four seasons, as under the current CBA a rookie's contract can last at most four years (including team options). Here, the expected value will be the player's total Win Shares in his first four years in the league. Using data from the 1977 through 2005 drafts, we get the following model:

EV = 26.5 - 6.3 * log(pick_overall)

Once again, using the fifth pick as an example:

EV = 26.5 - 6.3 * log(5) = 16.4

On average we would expect the fifth pick in the draft to produce about 16.4 Win Shares in his first four seasons. Let’s take a closer look at all of the fifth overall selections from 1977 through 2005:

+------+----------------------+------+
| year | player               | ws   |
+------+----------------------+------+
| 1977 | Walter Davis         | 36.0 | 
| 1978 | Purvis Short         | 16.5 | 
| 1979 | Sidney Moncrief      | 40.9 | 
| 1980 | James Ray            | -0.3 | 
| 1981 | Danny Vranes         | 11.7 | 
| 1982 | LaSalle Thompson     | 18.3 | 
| 1983 | Sidney Green         |  6.7 | 
| 1984 | Charles Barkley      | 45.8 | 
| 1985 | Jon Koncak           | 13.2 | 
| 1986 | Kenny Walker         | 14.6 | 
| 1987 | Scottie Pippen       | 22.6 | 
| 1988 | Mitch Richmond       | 24.2 | 
| 1989 | J.R. Reid            |  8.5 | 
| 1990 | Kendall Gill         | 16.3 | 
| 1991 | Steve Smith          | 20.5 | 
| 1992 | LaPhonso Ellis       | 17.0 | 
| 1993 | Isaiah Rider         | 12.1 | 
| 1994 | Juwan Howard         | 20.4 | 
| 1995 | Kevin Garnett        | 27.1 | 
| 1996 | Ray Allen            | 26.9 | 
| 1997 | Tony Battie          | 10.0 | 
| 1998 | Vince Carter         | 36.4 | 
| 1999 | Jonathan Bender      |  3.4 | 
| 2000 | Mike Miller          | 18.0 | 
| 2001 | Jason Richardson     | 17.8 | 
| 2002 | Nikoloz Tskitishvili | -1.6 | 
| 2003 | Dwyane Wade          | 38.5 | 
| 2004 | Devin Harris         | 18.2 | 
| 2005 | Raymond Felton       | 12.4 | 
+------+----------------------+------+

Seventeen of these players exceeded their expected value and twelve fell short.

Here is the value chart for all of the draft picks:

+------+------+
| Pick | EV   |
+------+------+
|    1 | 26.5 | 
|    2 | 22.1 | 
|    3 | 19.6 | 
|    4 | 17.8 | 
|    5 | 16.4 | 
|    6 | 15.2 | 
|    7 | 14.2 | 
|    8 | 13.4 | 
|    9 | 12.7 | 
|   10 | 12.0 | 
|   11 | 11.4 | 
|   12 | 10.8 | 
|   13 | 10.3 | 
|   14 |  9.9 | 
|   15 |  9.4 | 
|   16 |  9.0 | 
|   17 |  8.7 | 
|   18 |  8.3 | 
|   19 |  8.0 | 
|   20 |  7.6 | 
|   21 |  7.3 | 
|   22 |  7.0 | 
|   23 |  6.7 | 
|   24 |  6.5 | 
|   25 |  6.2 | 
|   26 |  6.0 | 
|   27 |  5.7 | 
|   28 |  5.5 | 
|   29 |  5.3 | 
|   30 |  5.1 | 
|   31 |  4.9 | 
|   32 |  4.7 | 
|   33 |  4.5 | 
|   34 |  4.3 | 
|   35 |  4.1 | 
|   36 |  3.9 | 
|   37 |  3.8 | 
|   38 |  3.6 | 
|   39 |  3.4 | 
|   40 |  3.3 | 
|   41 |  3.1 | 
|   42 |  3.0 | 
|   43 |  2.8 | 
|   44 |  2.7 | 
|   45 |  2.5 | 
|   46 |  2.4 | 
|   47 |  2.2 | 
|   48 |  2.1 | 
|   49 |  2.0 | 
|   50 |  1.9 | 
|   51 |  1.7 | 
|   52 |  1.6 | 
|   53 |  1.5 | 
|   54 |  1.4 | 
|   55 |  1.3 | 
|   56 |  1.1 | 
|   57 |  1.0 | 
|   58 |  0.9 | 
|   59 |  0.8 | 
|   60 |  0.7 | 
+------+------+

Armed with this information we can analyze past drafts and determine the biggest busts, the biggest surprises, and much more. Later this week, that's exactly what we'll do.

This entry was posted on Monday, June 22nd, 2009 at 1:32 pm and is filed under NBA Draft. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.