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Inside the Numbers: Scoring effectively

Ken Pomeroy's diatribe on the uselessness of overall FG percentage as a statistic in the three-point line era got me thinking: Are Big Ten teams doing themselves a favor with their current shot selection?

Heeding Pomeroy's advice, I examined a few more meaningful shooting metrics.

First some background on my assumptions. Bo Ryan is one of many coaches who stresses scoring at least one point per possession (PPP). This is considered the break-even point for the average team -- scoring more than 1.00 PPP is desired. To achieve this threshold, the baseline for your shooting percentages should be 50% on 2-point attempts and better than 33% on 3-point attempts because the efficiency of taking 100 shots of each kind would both be around 1 PPP in theory (TPPP)*.

Since effective field goal percentage (eFG%) accounts for the higher value of 3-pointers, comparing a team's eFG% to its 2-point FG% is a simple way to evaluate whether that team is executing its game plan well or if it would be smarter to change its approach. It's no surprise, based on the baselines we just established, that the national average for 3-point shooting percentage is exactly 33% at the moment. So any team shooting more threes than the national average with a lower eFG% than 2P% seems, well ... dumb.

Since Wisconsin and Michigan play tonight, here's a look at them first. The full conference breakdown is after the jump:

Shooting TPPP
Team eFG% 3P% 2P% 3PA/FGA 3Pt 2Pt Status
Michigan 51.5 34.2 51.7 43.8 1.026 1.034 Dumb
Wisconsin 52.2 37.1 49.8 41.2 1.113 0.996 Smart

So let's pick on Michigan. The Wolverines shoot a mediocre 34.2% from outside the arc and a pretty decent 51.7% on their 2-point attempts. But they are effectively shooting only 51.5% because they take so many 3-pointers. Theoretically, it would be better for Michigan to shoot 100 2-pointers (1.034 TPPP) than 100 3-pointers (1.026). Yet the Wolverines insist on taking shots from long distance 43.8% of the time, the 12th-highest rate in the country.

On the other hand, others have joined me in griping about how many 3-pointers the Badgers are taking these days. But there is not much to complain about: Wisconsin is wisely shooting more threes because their 3P% far outweighs their 2P%. But no one in the league appears as "smart" as Northwestern in that regard. Nerds ...

Shooting TPPP
Team eFG% 3P% 2P% 3PA/FGA 3Pt 2Pt Differential (%) Status
Illinois 54.5 42.3 50.6 30.0 1.269 1.012 0.257 (20%) Dumb
Indiana 54.7 38.3 53.4 32.6 1.149 1.068 0.081 (7%) OK
Iowa 48.8 34.0 47.8 29.9 1.020 0.956 0.064 (6%) OK
Michigan 51.5 34.2 51.7 43.8 1.026 1.034 -0.008 (-1%) Dumb
Michigan State 51.6 37.9 48.9 33.6 1.137 0.978 0.159 (14%) OK
Minnesota 51.2 34.0 51.3 30.6 1.020 1.026 -0.006 (-1%) OK
Northwestern 55.9 41.9 51.4 39.0 1.257 1.028 0.229 (18%) Smart
Ohio State 57.4 39.9 56.2 33.0 1.197 1.124 0.073 (6%) OK
Penn State 48.5 32.9 47.9 35.1 0.987 0.958 0.029 (3%) Eek!
Purdue 51.8 38.1 49.1 33.9 1.143 0.982 0.161 (14%) OK
Wisconsin 52.2 37.1 49.8 41.2 1.113 0.996 0.117 (11%) Smart

Yeah, that's right, I called Illinois' approach dumb. The Illini's shot selection could be smarter. I get it, in real life there's a diminishing rate of return on 3-pointers and Illinois would not maintain such a sterling 3P% if it were to jack them up all the time. But a few more here and there might help when you are shooting 'em at a 42.3% clip (1.269 TPPP). Just a thought.

These stats cannot tell the whole story of course, and some of the conclusions are obvious. Poorer shooting teams in general are playing from behind more often, which can account for the higher portion of their shots coming from downtown. Also, I could have taken free throw rate into account since missed field goal attempts do not count when there's a foul. And obviously more fouls are drawn when shooting 2-pointers than 3-pointers. But I didn't worry about that.

The other caveat worth mentioning is that the midrange range jumper is an endangered species in basketball thanks to the 3-point line. So while the national average in 2010 is slightly above our 33% threshold (34.3% = 102.9 TPPP), the average for 2-pointers is well below 50% (47.6% = 95.2 TPPP).

*TPPP = theorectical PPP based on 100 attempts exclusively from 3-point range or exclusively from 2-point range.
Updated table data to include games from 1/4/11.