The NBA started preventing high school stars from jumping straight to the league in 2005, requiring that entrants to its draft be at least 19 years old during the draft’s calendar year and one NBA season to have elapsed since the player graduated from high school (also known as the “one-and-done rule“).

Since 2006, only 68 players have made the leap after finishing their freshman year, a path Duke’s Jahlil Okafor, Kentucky’s Karl-Anthony Towns and Ohio State’s D’Angelo Russell will almost certainly take. However, not all have been successful in the NBA.

According to the metric win shares per 48 minutes, a one-and-done player selected in the top five is almost twice as effective at the NBA level than those in the bottom half of the top 10 and beyond. And the drop off from the first five picks to the next five is much more severe than their peers.

Using more traditional metrics like points, assists and rebounds per game shows the same trend in production as you get deeper in the draft.

Just 20 of the 68 one-and-done players selected have produced at an above-average clip (0.100 WS/48 or higher), a group that includes Anthony Davis, Kevin Durant, Kevin Love and John Wall.

The latest mock NBA drafts have Okafor and Russell selected in the top five, but Kentucky’s Trey Lyles and Duke’s Tyus Jones are projected to be taken after the No. 10 pick, suggesting their new teams could be facing disappointment.