This week, the TAB's over/under markets went up well before Centrebet's, and Centrebet released theirs over an extended period, which means that the data in the table below spans an atypically long timespan since each market has been recorded as close to its opening as I was able.
The main difference this has produced is a 7-point gap between the TAB's and Centrebet's margin in the Port Adelaide v Fremantle game.
That aside, we see only a couple of points - at most - difference between the two bookmaker's Totals and similarly sized differences in their implied team scores.
Both bookmakers have the Hawks v Crows, and GWS v Gold Coast games as the round's likely highest-scoring contests, and the Port Adelaide v Fremantle game as the likely lowest-scoring. MoSSBODS and MoSHBODS disagree with the bookmakers about which game will be highest-scoring, preferring instead the Lions v Dons game, and disagree too about which will be lowest-scoring, opting for the Dogs v Swans matchup.
All four agree that the Giants are likely to be the round's highest-scoring team, but only MoSSBODS, MoSHBODS and Centrebet have the Dockers as low scorers, while the TAB casts Carlton in this role.
MoSSBODS has the average total per game coming in at 184 points, MoSHBODS at 185 points, the TAB at 188 points, and Centrebet at 189 points.
MoSSBODS' different opinions have seen the Over/Under Fund make four wagers this week, three on unders and two on overs.
For two of those bets, the apparent overlay is fairly high: about 3 goals in the Dogs v Swans game, and 13.5 points in the Lions v Dons game. The overlays in the Cats v Roos, and Dees v Blues contests are a bit smaller and around the 1 to 2-goal mark.
MoSSBODS has seven of the home teams scoring fewer points than do TAB and Centrebet, but only three or four of the away teams doing the same.
In the table below we look at MoSSBODS', MoSHBODS' and the two bookmakers' performances in Round 1 compared to actual scores.
On the right of the table we have the forecasters' mean absolute errors (MAEs), which shows that:
- The TAB had the most accurate margin estimates (MAE of 32.3 points per game). Centrebet (32.5 points) were next best, and MoSSBODS (35.6) was more accurate than MoSHBODS (38.1).
- MoSSBODS was most accurate in estimating home team scores (MAE 14 points per game). MoSHBODS and Centrebet were both, equally, next most accurate (15.7 points per game).
- The TAB was most accurate in estimating away team scores (MAE 22.4 points per game), ahead of Centrebet (22.6), MoSSBODS (24.7), and then MoSHBODS (26.6).
- Centrebet was most accurate for totals with an MAE of 28.9, but even the worst performer, MoSHBODS, was only 0.6 points per game behind.
Looking at the left-hand side of the table, which provides raw error data (in terms of actual less expected scores), we see that all four forecasters overestimated home team margins despite underestimating home team scores. This was because they all underestimated away team scores even more. They also all underestimated total scores by about 28 to 29 points.