We chose to measure a player's value using John Hollinger's estimated wins added (EWA) statistic. Simply put, EWA measures how many wins a player adds to his team's record compared to someone you could sign to a 10-day contract (to put it nicely, a replacement-level player). Basically, the metric combines player efficiency rating (how efficient a player is on a per-minute basis) with playing time and comparative value. Hollinger offers a far more detailed explanation, but for our purposes, just remember that EWA measures wins added and that LeBron James led the league at 32.3.
Most important, it's a great way to objectively assess a player's worth -- in this case, in order to evaluate draft picks. So, our first step was to collect the career EWA for every player drafted over the past 20 years. Then we adjusted that total into a per-season value (EWA/season), in order to illustrate what kind of contribution each player made on a seasonal basis. We want to account for longevity in addition to productivity, so the "season" part of the equation is not simply the number of seasons played. Instead, we measured the number of seasons since a player was drafted, capped at a maximum of 15, which benefits guys with longer careers.
Confused? These two examples should straighten things out. First, take Greg Oden. A knee injury shelved him for what would have been his rookie season in 2007-08. Because other teams received immediate contributions from players in that draft, his absence can't be ignored. Therefore, his current EWA must be divided by two, giving him a rating of 2.45 wins added, rather than the 4.9 he produced this season. The longer he plays, the more that empty season will be discounted.
Similarly, Dino Radja, whom the Celtics drafted in 1989, ended up averaging 16.7 points over four productive seasons, for a total EWA of 23.23. But he wasn't as valuable as Dana Barros, who was drafted the same season. Even though Barros's career scoring average was just 10.5, he spent 14 years in the league, providing a longer-lasting impact and an adjusted EWA of 3.51, well ahead of Radja's 1.55.
Also, an international player who joins the league several years after being drafted, such as Luis Scola, does not (and should not) receive as much credit as one who plays immediately, like Andris Biedrins.
And yes, it's possible to produce a negative EWA. If a player doesn't appear in a single game, his value to his team is his roster spot, which is equivalent to adding a replacement-level player. That's why his EWA would be zero. But if a player is so inefficient (missing shots, committing turnovers, etc.) that he ends up with a negative EWA, he has, in essence, cost his team wins. Lottery picks tend to get longer leashes for mistakes, which helps explain Michael Olowokandi's -0.2 adjusted EWA. His contributions were remarkably poor for the No. 1 overall pick in the 1998 draft, but he was given ample opportunities to justify the selection. Needless to say, he failed.
Once we calculated every player's adjusted EWA, we entered the final phase of the process: developing a method of comparison. We were able to come up with an expected EWA for each pick number by averaging the rating for everyone selected at that slot over the past 20 years. From those numbers, we could then run a regression analysis in order to rate the draft as accurately as possible while making the value of each pick greater than the next. (In other words, the ninth pick actually outperformed the eighth over the past 20 seasons, but that doesn't mean there's any advantage in picking lower in the draft.)
The results have both conformed to conventional wisdom and been shocking in their revelations. For instance, you would expect talent to drop off after the fifth pick, but the degree of that slide is remarkable. Also, we expected the middle of the first round to be unpredictable, but didn't anticipate that it was more likely for teams to draft a scrub than a useful player. We'll elaborate on these findings in the coming weeks, as we attempt to determine, once and for all, the value of the NBA draft.