Efficiency margin, a little-used stat, says Terps near top of the ACC
As Maryland ventures through the final two weeks of the regular season, it will do so as one of the most efficient teams (per possession) in the ACC. We've discussed on many occasions this season how potent the Terrapins have been on offense this year, how crisp their execution has been most of the time and how that portends well for the down the line. But in terms of quantifying Maryland's efficiency level, this forum had relied solely on observations and stat lines.
The folks at Basketball Prospectus, however, have used a decades-old, yet seldom-used, formula to determine precisely how efficient Maryland has been this season. Using a measuring stick first used by Dean Smith during his days roaming the sidelines at North Carolina, Basketball Prospectus has calculated that the Terrapins possess an efficiency margin of plus-0.11, which ranks second in the ACC behind Duke (plus-0.16).
What, exactly, constitutes a team's efficiency margin? According to John Gasaway, a writer for Basketball Prospectus, it's a calculation that measures a team's points per possession against the points per possession tallied by its opponents.
"A college basketball game is going to have something between 50 possessions if it's really slow, or 75, 80 on the other hand if it's really fast," Gasaway said. "The only way to make sense of any of the stat totals in there is if you know which of those extremes the game was played at."
For instance, Maryland is averaging 68.6 possessions per game in ACC play this season (the sixth-highest average among ACC teams) and is scoring 1.08 points per possession. The Terrapins' opponents, meantime, are scoring 0.97 points per possession. Simple subtraction (points per possession minus opponents' points per possession) gives Maryland a plus-0.11 efficiency margin.
"Of course, it all depends on the quality of your opposition, but speaking of major-conference teams, if they are playing conference games against opponents in their own league, generally speaking, if you score one point or better per possession, that's good," Gasaway said in a telephone interview. "If you score 1.1 point per possession, that's great. And if you score 1.2, that's simply stratospheric, out of this world, historic, fantastic. That would be a general rule of thumb."
In case you're curious, here are the efficiency margins of each ACC team:
1) Duke -- plus-0.16
2) Maryland -- plus-0.11
3) Clemson -- plus-0.05
4) Virginia Tech -- plus-0.03
5) Florida State -- plus-0.02
6) Wake Forest -- 0.00
7) Georgia Tech -- minus-0.01
8) Virginia -- minus-0.03
9) North Carolina -- minus-0.08
10) Boston College -- minus-0.08
11) NC State -- minus-0.09
12) Miami -- minus-0.10
And here are the points per possession averages of each ACC team:
1) Duke -- 1.11
2) Maryland -- 1.08
3) Virginia Tech -- 1.00
4) Wake Forest -- 1.00
5) Boston College -- 1.00
6) Miami -- 1.00
7) Florida State -- 0.99
8) Clemson -- 0.98
9) Georgia Tech -- 0.98
10) Virginia -- 0.97
11) NC Stae -- 0.97
12) North Carolina -- 0.96
How far has North Carolina fallen this season? Well, last year the Tar Heels led the ACC in efficiency margin (plus-0.15) and in points per possession (1.16). North Carolina then went on to win the national title. This season, UNC is at or near the bottom of the league in both categories. Yikes.
So what do all these numbers mean? Well, Gasaway says they can be used to help predict how a team will fare in the NCAA tournament. He said Maryland, for instance, will be ranked too low if it receives the No. 7 seed many prognosticators currently are giving them. According to Gasaway, the Terrapins are comparable to Purdue (plus-0.11 efficiency margin) and Syracuse (plus-0.11).
But are the efficiency margins of teams from different conferences comparable, given that these calculations are based purely on how teams fare against foes from only their specific conference?
"It is tricky," Gasaway said. "You're dealing with teams that are playing two entirely different sets of opponents. But what I would offer based on a couple of years of working with this stuff is that generally speaking, and, you know, with the case of the Pac-10 this year or the SEC last year, they need an asterisk by them. They constitute exceptions.
"But generally speaking, the differences in quality of play between these top six major conferences are really not going to be very great. We tend to invest a lot of discursive and polemic energy into questions like is the ACC better than the Pac-10? Or is the Big 12 better than the ACC? And it's fun to do. I'm not above doing that myself, but if you look at the wide sweep of college basketball, you can fit those top six conferences qualitatively into about an inch. Then the rest of the conferences below them, that takes in more of one or two or even three feet of qualitative space, so the difference between teams in different conferences, you know, their relative levels of performances is going to usually be a larger difference than the quality of the opposition. But it's something you definitely have to be careful about."
Last season, Maryland owned a minus-0.07 efficiency margin entering the postseason and then proceeded to defeat California (plus-0.02) in the first round of the NCAA tournament. The Terrapins fell to Memphis (plus-0.27) in the second round, though the Tigers' rating surely was inflated by its far inferior competition in Conference USA. For a look at the efficiency margins of other teams at the conclusion of the regular season last year, click here.
As for the ACC this season, Gasaway said he is not as down on the conference as are many other observers, primarily because of the performance of the teams at the bottom of the standings.
"Well, the ACC is down in the sense that they don't have that critical mass of, say, two or even three great teams that are big and scary and that everybody points to," Gasaway said. "Ironically, by some measures, the ACC, however, is actually the strongest conference in the country for the exact opposite reason. It's also true that they don't have any really bad, struggling teams.
"The teams at the bottom of the conference like Miami or N.C. State, whoever you want to pick, are clearly superior to comparable bottom-of-the-conference teams, such as DePaul or Nebraska or Indiana. And that's not a part of the conference that people usually look at, but when you're talking about a season's worth of conference games and then trying to come up with a number for the quality of the competition, when you've got zero really bad teams and you never play a really bad team, that means your strength of schedule is actually good."
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