While Tracy McGrady and Kobe Bryant are busy making it a two-horse race for the title of the league's most prolific scorer, another question remains unanswered: Who is the league's most efficient scorer? In other words, who gets the most out of his shot attempts?

At first, one might look to field-goal percentage to answer this question. Shaquille O'Neal is running away with the league lead at 55.9 percent. So does that settle it? Not exactly.

For one thing, the top 10 in field-goal percentage consist entirely of forwards and centers. There are no guards because they're the ones taking all the 3-point shots, which are lower percentage but worth an extra point. Shooting 38 percent on those, for instance, is better than as Shaq shooting 55.9 percent on lay-ups and dunks.

For another, there are free throws. Shaq spends huge chunks of the game at the line, where he hits just 61 percent of his tries. Perhaps a player with a lower field-goal percentage but a more respectable mark from the line is actually more effeicient.

To settle this, I created a stat called points per shot attempt, or PSA. To compute it, take free-throw attempts and multiply by 0.44, then add field-goal attempts. Take the player's points and divide by that number, and you're done:

PSA = Points / (FGA + (FTA *0.44))

(Why multiply by 0.44? Because one free throw attempt is equivalent to 0.44 field goal attempts. It would be 0.5 exactly if every foul resulted in two shots, but one-shot fouls after made baskets, technical fouls and lane violations bring the number down.)

So enough with the numbers already. Who are the best?

Here's this year's top 10 in PSA:

In fact, most of the players on the list above are third options or worse for their teams. While all of them have been fantastic when they get opportunities, none is among the game's elite scorers. As a result, let's modify the top 10 list a bit by restricting it to players who are averaging 15 or more points per game:

Looking closer at the last two charts, Dallas' three international N's: Najera (Mexico), Nowitzki (Germany), and Nash (Canada), go a long way toward explaining why the Mavs have such a deadly offense. The two featured players, Nash and Nowitzki, are in the top seven in the league in PSA among players averaging 15 or more; meanwhile, Najera easily has the highest PSA in the league. Shawn Bradley just missed being in the top 10 as well.

But enough about the good guys. I know what you're thinking already: What about the worst guys? I won't disappoint you. Here's the NBA's bottom ten in PSA among players who have played at least 500 minutes:

The Nuggets are on pace to be the worst offense in NBA history, so it's no surprise that they also placed two players in the bottom five. Rookie point guard Junior Harrington has struggled from the field and the line en route to the third-worst mark. But the guy who might have the most to worry about is rookie forward Nikoloz Tskitishvili. An alleged shooter, his putrid 29.2 percentage has raised eyebrows among Nuggets fans wondering why he was picked ahead of Amare Stoudemire.

Yet the bottom list is a bit disappointing as well, because it's made up of players that we already knew couldn't play. What we really want to find out is who, among the NBA's prominent scorers, isn't cashing in enough of their shots? To answer that, I limited the following list to players averaging 10 or more points per game:

Two more surprising names on the list are Antoine Walker and Vince Carter. Walker has been just as erratic as ever from the field this year (a career-low 39 percent), and has also hurt himself with a free-throw mark that has plummetted to 61.9. Carter, meanwhile, has compounded his low-percentage shooting by making himself a rare visitor to the free-throw line. He takes nearly six field-goal attempts for every free throw, clobbering his PSA in the process.

Overall, PSA is superior tool to field-goal percentage because it also takes in 3-point shooting and free-throw success. While accurate shooters shouldn't necessarily be featured scorers -- I don't imagine the Mavs are drawing up plays for Najera right now -- it does reflect which players make the most of their scoring chances.