2018 - Round 15 : Overs/Unders Update

The Melbourne v St Kilda game is this week's best hope at producing a total over 170 points according to all four of our forecasters, though in the case of the two bookmakers it's the only game of the nine more likely than not to do so.

For the most part, the MoS twins broadly agree with the bookmakers this week, with the absolute difference in expected totals no larger than 11 points in any of the nine games, and with opinions about the likely low- and high-scoring teams completely aligned.


  • All : Melbourne v St Kilda (173.5 to 178)


  • All : Carlton v Port Adelaide (148 to 156.5)


  • MoSSBODS & MoSHBODS : Collingwood (109 to 110)
  • TAB & Centrebet : Melbourne (106 to 107)


  • MoSSBODS & MoSHBODS : Gold Coast (58 to 60)
  • TAB & Centrebet : Carlton (57.5 to 59)

MoSHBODS did somewhat better than a naive forecasting in selecting the extremes of team and game scoring last weekend, attaching:

  • 11.0% probability to the highest-scoring team, GWS (against a naive forecast of 8.5% since 12 teams were playing)
  • 38.4% probability to the lowest-scoring team, Gold Coast (against a naive forecast of 8.5%)
  • 19.0% probability to the highest-scoring game, Brisbane Lions v GWS (against a naive forecast of 16.7% since 6 games were played)
  • 13.7% probability to the lowest-scoring game, West Coast v Essendon (against a naive forecast of 16.7%)

This week, MoSHBODS has

  • five teams as more likely than 1 in 18 to be the highest-scoring: Collingwood, Melbourne, Fremantle, Port Adelaide and West Coast.
  • six teams as more likely than 1 in 18 to be the lowest-scoring: Carlton, Gold Coast, Western Bulldogs, Sydney, Hawthorn and St Kilda.
  • five games as more likely than 1 in 9 to be the highest-scoring: Dees v Saints, Dockers v Lions, Suns v Pies, Bombers v Roos, and Crows v Eagles.
  • four games as more likely than 1 in 9 to be the lowest-scoring: Blues v Power, Giants v Hawks, Dogs v Cats, Tigers v Swans.

It's something of a low bar just to hope that MoSHBODS can do better than blind-guessing in these markets, but let's start with that as an initial goal. So far this season it's exceeding that goal when predicting high- and low-scoring teams, but not when predicting high- and low-scoring games.

(It might be, of course, that the bookmakers are doing no better than chance either, but I don't have the data to test that hypothesis and my firm prior would be that this is unlikely.)


Investors face only three wagers this week, two overs and a single unders. For the Suns v Pies game, where one of the overs wagers has been placed, the current forecast is for showers, while for the other overs wager the forecast is irrelevant since the game is being played at the beroofed Docklands Stadium.

The lone unders wager is expected to be resolved in fair weather (but, it's in Melbourne, in June, so there's always a chance).

As alluded to earlier, overlays are generally small this week, and all are less than 2 goals. MoSSBODS and MoSHBODS have done fairly well this season, however, when the estimated overlays have been small, though only when those overlays have suggested an unders wager.

R15 - Overlay v Performance.png

For example, MoSHBODS has been right 68% of the time when its expected game total has been 0.1 to 6 points under the Centrebet total. MoSSBODS has been right 63% of the time when its expected total has been similar in relation to Centrebet's, though its rules of engagement have prohibited it from betting in these circumstances.

One factor influencing all of the numbers we see in this table is the fact that 66% of games this season have finished as unders for both the TAB and Centrebet. 


MoSSBODS finished on the correct side of the TAB's totals in two of the six games last weekend and only one of Centrebet's, while MoSHBODS finished on the correct side of both bookmakers' totals in two games.

That left MoSSBODS' with a season-long 49% record against the TAB and a 48% record against Centrebet, and left MoSHBODS with a 47% record against the TAB and a 50% record against Centrebet.

MoSSBODS' landed 1 of 2 unders bets with the TAB last weekend, and 0 of 2 overs bets with Centrebet. Its overall strike rate on overs bets in now just 27% and on unders bets 62%.

On the mean absolute error (MAE) metric, MoSSBODS registered the lowest MAE for game margins and away team scores this week, MoSHBODS for home team scores, and Centrebet for game totals. 

Centrebet still leads, however, on the season-long view for home team scores and game totals, while the TAB now leads outright on game margins and also continues to lead on away team scores.