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October 17, 2007
Hometown Scoring
How Many Assists Did Acie Law Really Have?

by Ken Pomeroy

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Sometimes, the most common statistics are taken for granted as being the truth. It's assumed that the numbers we use represent an accurate historical record but occasionally they do not. Anyone who has ever tried to do a little scorekeeping on their own has surely experienced the frustration of trying to keep up with the action. Even the basics like points and rebounds are not easy to keep accurately. Official scorers in college basketball are no different, except that they have to record much more than points and rebounds.

Though the scoring operation at a Division I game is sophisticated, there are still errors made. In large part, these are random errors. Perhaps on rare occasions a basket is assigned to the wrong player, and a little more frequently a rebound is given to someone erroneously. Just because Player A gets an extra rebound credited to him in a game, however, doesn't mean he'll see his rebound totals inflated consistently the rest of the season. This was just an unintentional error of an otherwise diligent scorekeeper.

The judgment stats are a little different. Some scorekeepers subconsciously employ a different definitions for a certain stats involving judgment like assists, steals and even blocked shots. Statistically, there is more variability in how scorekeepers track assists than any other basic basketball statistic.

Pages 28 and 29 of The Official NCAA 2007 Basketball Statistician's Manual (warning: PDF) defines an assist for college basketball:

A player is credited with an assist when the player makes, in the judgment of the statistician, the principal pass contributing directly to a field goal (or an awarded score of two or three points)... Philosophy. An assist should be more than a routine pass that just happens to be followed by a field goal. It should be a conscious effort to find the open player or to help a player work free....

The manual goes on to detail some scenarios that further clarify when an assist should be awarded. It's fairly specific, and it is comprehensive about defining an assist, although in the end there is still some room for interpretation. After reading the manual, I concluded that there's not as much room for judgment as one might have thought. In most cases, the process of awarding an assist is standard across college basketball.

With biased errors, unlike random errors, there are ways to sort out where the biases exist, and whom those errors benefit. In this case, we can compare how often a team is credited with an assist at home to how often they get an assist away from home. Since scorekeepers are largely the same people at each home game, we can single out which teams have scorekeepers that ration assists like they're gold and those that make even the most selfish players look like Steve Nash.

The most generous scorekeepers were associated with the following five teams in 2007:

Assist Percentage (A/FGM)
                   Home     Away 
Texas A&M          78.5     45.2
Sam Houston St.    82.6     55.0
Evansville         72.1     47.3
South Florida      74.9     52.1
Cal St. Fullerton  69.0     47.9

It turns out that the king of assist bias is the table at Texas A&M. At home, the Aggies recorded assists on 78.5% of their made field goals. It's a percentage that is ridiculous to the point of being unbelievable. Only one team in the country cleared an assist rate of 70% on the season and that was Northwestern at 71.6%. A&M did play some cream puffs at home, so perhaps a figure close to 80% could be attained over 19 games, which was the length of their home schedule.

Any hope of suspending disbelief is lost by knowing that away from Reed Arena, A&M was credited with assists on just 45.2% of their made baskets. That figure is significantly below the national average assist rate of 55.1%. It's a rate that, sustained for the entire season, would have ranked Texas A&M 323rd--14th-worst--in the country in sharing the basketball. So to summarize: At home, Texas A&M was one of the best assisting teams in college basketball history. Away from home, they were the worst major conference team in sharing the ball.

Away from home, A&M was playing in front of all sorts of different scorekeepers, so it's unlikely that there was a conspiracy among all or even most of them to not record Aggies' assists. No, the only explanation is that assist inflation was at record levels in College Station in 2007. It was a phenomenon that didn't go unnoticed in the rest of the conference. Texas took the unusual step of voiding assists that were credited to its own team in a game at Texas A&M. (Note: under NCAA rules this a step that doesn't affect the official statistics, only Texas' internal records.)

So how many assists did the Aggies really have? Let's use their road assist percentage as a guide. The average NCAA scorekeeper gives the home team five more assists per 100 made field goals than he/she gives the opponent. This could be real, but it's probably not. You wouldn't think there would be a home-court advantage for passing, especially since we are accounting for the number of field goals made in this study. If we evenly distribute that 5% bias between the home and road team, Texas A&M's true assist percentage on the road was 45.2% +2.5%, or 47.7%. If we assume this was their true assist percentage in all games, then we can apply that figure to the 908 field goals A&M made for the season. This yields a "real" assist total of 433--158 fewer than were actually recorded.

Now to the question that is the basis for this article. Applying this reduction equally to each A&M player would reduce Acie Law's assist total from 169 to 124, or from 5.0 per game, ranking 63rd in the nation, to 3.6 and out of the top 200. Law was credited with a career-high 15 assists in A&M's home win over Texas in February. We don't know how many he really had, but it's safe to say that 99% of NCAA scorekeepers would have recorded a lower number.

Before wrapping this up, it's only natural to look at the opposite end of the spectrum. While on balance, there's a tendency for home scorekeepers to give their players an assist boost, this isn't true everywhere. The folks with the strictest definition of an assist:

    Assist Percentage (A/FGM)
                   Home    Away
New Mexico St.     46.3    60.1
Northern Colorado  50.9    60.6
Lafayette          57.7    67.1
Illinois           57.8    66.0
Long Island        42.3    50.4

Nobody was stingier about doling out assists than the table at the Pan American Center, where they ignored about one out of every four assists that their counterparts in other arenas were counting. This means that New Mexico State point guard Elijah Ingram was better at setting up his teammates than his stats suggest. Officially, he had 35 assists at home. Had he recorded assists at the rate he did on the road, he would have had 47 home helpers.

That might not seem like a dramatic difference, but you can really get a feel for how subjective assists are by magically trading the Aggie scorekeepers in College Station for the ones in Las Cruces. If we could do that, our best estimate of Ingram's home assist total would have it increasing to 78, or more than doubling. His assist rate for the season would have risen from 17.3% to 26.4%, or from a below-average playmaker to a respectable one, ranking him just outside the top 150 nationally. Similarly, Law's assist rate would have decreased from 30.8% to 19.7%, making him look like a score-first point guard--which is closer to the truth.

For the most part, scorekeepers across the nation have a similar view of an assist. As long as D-I nation spans more than 300 teams, however, there will be outliers. In this case, it may have influenced the view of Acie Law's and Elijah Ingram's talents. More than likely, Ingram was better at setting up his teammates, even though the stats indicate that Law was easily the better assist man. There is no statistic in major sports as subjective as the basketball assist, and we should consider that before reading too much into a player's or team's assist rate.

Ken Pomeroy is an author of Basketball Prospectus. You can contact Ken by clicking here or click here to see Ken's other articles.

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