Posts Tagged ‘Betting’

2017 Expt Wins

January 22, 2018

So in what is now becoming an annual exercise let’s review the 2017 season through the prism of Expected Wins (Expt Wins).The 2015 and 2016 versions of this article can be found here and here

For the uninitiated Expt Wins uses bookmaker’s odds (note 1), as a sort of independent arbiter, to see which teams over (or under!) performed versus what was expected on a game by game basis. It is a much better fairer view than sheer win percentages given (a) how relatively short the season is for most teams and (b) how uneven the Championship can be in terms of the quality of teams facing off against each other.

Table 1; 2017’s best and brightest

Unsurprisingly the top10 is peppered with teams that were promoted. This makes sense as for the majority of teams the league makes up at least two thirds of their season.

Carlow had an excellent season – but it was no fluke; they were also top5 in 2016. Over the past two seasons they have won 11 games when they were only expected to win ~7.7. And they managed to top the 2017 table despite losing as 1/16 home favourites against London. 1/16, without accounting for the bookmaker’s margin (see note1), implies a 94% win probability. Win that game and their “above Expt Wins” total would be twice that of second placed Louth. That loss is the shortest price loss in the database and must be one they desperately want back. There is no guarantee that Carlow would have gained promotion had they beaten London – as Wexford no doubt would have put greater emphasis on their final two games – but they must be absolutely kicking themselves every time they think of that game. And yet – they still topped the 2017 table despite this loss.

Now I am by no means an expert on the ins and outs of Louth football – and you have to think they have a good ‘un in Pete McGrath – but you have to feel for Colin Kelly. Back to back promotions. A 59% win rate over that period which lands them 5th on that metric behind the likes of Dublin, Tyrone, Kerry and Kildare (themselves aided by back to back promotions) and along with Carlow the only team to finish in the top5 Expt wins both years.

The two Championship campaigns were poor in comparison (played 6 won 3 with three loses of 4, 6 and 9 when stepping up against Derry and Meath) but still … be careful what you wish for.

In 2016 Tyrone and Cavan were in the top10 following successful promotions from Division2 and the trend holds true for Galway and Kildare. Division2 is always very tight – just under half (27 of 56) of all games in the last two years had a zero or one point handicap. Extend that to two points and 80% of the games are covered. Win enough games to gain promotion in these tight contests and you are well on your way to outperforming expectations for the season.

Table 2; 2017’s laggards

This is a mixed bunch of
1. Division4 teams who struggled to register wins and who are perennially down the bottom of these rankings – Limerick, Waterford, Wicklow
2. Teams that had a disastrous season – Cavan, Laois, Derry
3. Very good teams that didn’t get the job done enough – Kerry & Mayo
4. Cork!

Taking the four cohorts in order

1. The worst team in 2017 was (subjectively) Wicklow but no matter how bad you are when you play your peers in the league you are always given “some” chance. Wicklow’s seven league appearances saw them chalked up at odds of 8/11, 3/1, 5/6, 10/3, 11/2, 6/5 and 6/1. When we remove the bookmaker’s margin that equates to an expectation of two wins. And that’s for the “worst team”. Limerick’s odds were 8/13, 11/10, 13/8, 1/10, 8/15, 11/8 and 1/10 which comes out at just over four wins.

No matter how poorly you are viewed under Expt Wins you will always be expected to notch up at least two wins and maybe four or five … if you struggle to win games full stop you will always be down the bottom end of this table.

2. All three of Cavan, Laois and Derry were relegated and whilst combined they won 4 of 10 Championship games three of those victories came against Division4 teams when they were heavily favoured. At a very high level this cohort win the games they are expected to win, lost the ones they were expected to lose and came out the wrong side of way too many 50:50 calls

3. Mayo being so low on the table is easy enough to explain; in the three games that they drew Mayo were 1/5, 1/6 and 23/10 – those three games alone account for their negative Expt Wins. Kerry are slightly different. They may have finally managed to beat Dublin in the Division1 final but outside of that they failed to win half their games – with three of those games coming against Mayo when a good favourite (2/5, 1/2 and 8/13). They were almost prohibitively favoured at 1/20, 1/5 & 1/6 in the three Championship games that they won. That mixture (winning when big favourite, losing/drawing when favouritism is less obvious) is a recipe for a poor Expt Wins season

4. Cork. Ah Cork. For the second year in a row they appear in the bottom5 but can you imagine how poor they would look had Waterford managed to tack on one more point when Cork were 1/50? Cork were middle of the pack on win ratio (winning 41% of their games) but were overturned by Tipperary as a 7 point favourite in the 2016 Championship whilst also losing at odds of 1/3, 4/11 and 4/11 over the two league campaigns. They never won a game as underdog to balance these losses.

Is it predictive?
Although there are outliers – notably Carlow, Louth and Cork – I would lean towards no. There is just too much volatility as teams yo-yo up and down the table; Kerry from 27th in 2015 to equal 6th in 2016 and then back down to 28th in 2017; Cavan from 9th to 31st, Armagh from 32nd to 5th. Good luck trying to pick which of this year’s top5 will stay there!

Note1; calculating Expt Wins

Using the All Ireland final as an example. Paddy Power’s odds for the game were Dublin 4/9, Mayo 3/1 with the draw being 9/1. All that these fractional odds are is another way of expressing probabilities. To work out the probability any odds equate to you use the following formula (B/ (A+B)). For Dublin’s 4/9 the B here = 9 and the A = 4 so the probability of a Dublin win = (9/ (4+9)) which equals 0.692 or 69.2%. Do this for all three odds and you get

Dublin = (9/ (4+9)) = 69.2%
Mayo = (1/ (1+3)) = 25.0%
Draw = (1/ (1+9)) = 10.0%

The total percentages add up to 104.2%. Now we know that there are only the three outcomes for any game – team1 wins, team2 wins and draw – so anything above 100% for these three outcomes is the bookmaker’s margin. To get a truer understanding of the probabilities we strip out the margin equally across the three outcomes and come up with an Expt Win for each team. Dublin in this instance = 67.8% or 0.678 (69.2%-((104.2%-100%)/3)); Mayo = 23.6% or 0.236 (25.0%-((104.2%-100%)/3))

Note2; the odds
All odds are taken from Paddy Power and tend to be taken towards the back end of the week (Friday night/Saturday morning) to let any movements settle down. It is possible that injury news etc. changes the odds between what was taken and what they were at throw in but I’m comfortable enough that this would be a rare enough occurrence not to have too big an impact.


Expected Wins – 2016 season

January 27, 2017

In 2015 we introduced the idea of Expected Wins (“Expt Wins”) which reviews a team’s season, on a game by game basis, versus what they were expected to do using bookmaker’s odds. There are undoubtedly drawbacks to this which are expanded upon in the original article (here) however it is an interesting prism to view the season through rather than just looking at those that had a “good Championship”

2016 Top Performers

Team Games played Wins Win % Expt Wins above/below Expt Pts Win % rank Expt Wins rank
Clare 14 9 64% 5.465 +3.535 5 1
Dublin 16 15 94% 12.218 +2.782 1 2
Longford 10 5 50% 3.430 +1.570 =11 3
Louth 11 7 64% 5.483 +1.517 6 4
Carlow 10 4 40% 2.750 +1.250 =18 5

As can be expected those teams that have a good winning percentage are also high up on the Expt Wins ranking. Keep winning and you’ll consistently outperform your odds and thus your Expected Wins. Dublin, despite their very short odds at times and thus very high Expt Win total, being the poster child for this.

The two teams that had the most unexpected run in the Championship – Clare and Tipperary – are both comfortably in the top10 (Tipperary are joint 6th with an Expt Win total of +0.889) as they made a mockery of their odds at times. Indeed Clare also had an excellent league campaign, winning five of their eight games and picking up the Division 3 title, which helped them climb to first in the table.

Longford had a lesser league campaign winning three of their seven games but completed one of the shocks of the Championship beating Monaghan away in the qualifiers at odds of 15/2 which accounted for nearly all their positive Expt Win total. Removing the bookmaker’s margin they were expected to win that game ~8% of the time.

Perhaps the biggest surprise is Carlow. They won three games in the league for the first time since 2012 (when there was an extra game as Kilkenny played boosting everyone’s win volume in Division4!) whilst also recording only their second Championship win since the end of the 2011 campaign. You won’t read about Carlow having a good season anywhere … but the fact they outperformed expectations to such an extent should ensure it is considered as such.

Versus the Handicap

Another way to review a team is through the prism of the handicap. Bookmakers will tell you that they set the handicap line according to what they think their customers will back, thus giving them an even book, rather than the respective merits of the teams. Public perception, along with the strengths of the team, thus feeds into the handicap line. Even still it is quite a good barometer of how teams are expected to perform. So how did teams fare against the handicap and also the two rankings above?

Team Games played Games covered Cover % Cover Rank Win % rank Expt Wins rank
Kerry 13 10 76.9% 1 =2 =6
Louth 11 8 72.7% =2 6 4
Fermanagh 11 8 72.7% =2 =20 11
Tyrone 13 8 61.5% =4 =2 =8
Cavan 13 8 61.5% =4 =10 9

Only Louth appear in the Top5 of both the Expt Win and Handicap rankings though in truth all 5 that covered the handicaps most often were also high up in the Expt Wins Ranking.

Fermanagh may have only won four of their 11 games in 2016 (two at home in the league, the home win versus Antrim in the Ulster Championship and then away to Wexford in the qualifiers) however they were a tough nut to crack with only 3 teams managing to beat them on the handicap (Cavan winning by 6 in Brewster Park, Derry in the opening round of the league and Donegal in the Ulster championship). Indeed that Cavan game was the only one of the five that Fermanagh played at home where they failed to cover the handicap. We saw something similar in 2015 when they covered in five of the six games played at home. Fortress Brewster!

But this all buries the lead. Kerry were excellent against the handicap (see Note1) where they only failed to cover in the opening two rounds of the league, against Dublin and Roscommon, and again in the league final. We have seen a phenomenon of double digit favourites tending not to cover (see Note2) but when a big favourite in 2016 (11 + 10 versus Clare in their two games and 9 versus Tipperary in the Munster final) Kerry covered each time. They don’t get dragged down by “lesser” opposition – they play to their own level.

2016 Worst Performers

Team Games played Wins Win % Expt Wins above/below Expt Pts Win % rank Expt Wins rank
Cork 11 5 45% 6.617 -1.617 15 28
Limerick 10 1 10% 2.799 -1.799 31 29
Monaghan 14 4 36% 5.829 -1.829 =20 30
Down 9 0 0% 1.960 -1.960 32 31
Armagh 10 2 20% 3.963 -1.963 29 32

It is no surprise, given that league games can make up 60% to 70% of a poor team’s season that relegated teams feature heavily here. Between them Cork, Down, Armagh & Limerick mustered five wins from their 28 league games.

Down didn’t register a win in 2016 however Armagh, despite winning two games, came out slightly worse on Expt Wins. This is due to the fact that they were expected to be competitive in Division2. Outside of the Round6 game away to Tyrone, when the reality of their form was beginning to catch up with their odds, the largest price they were in any league game was 7/4. They also played three (see Note3) Championship games where they were given a good chance of winning each (2/1, 11/10 & 9/4) but came away with three losses.

Down on the other hand started slowly and continued to plummet. They may have lost all nine games but were only ever expected to win ~1.96 of those. Armagh were expected to win ~3.96 of theirs.

Monaghan had an average league campaign winning three of their seven games when they were expected to win ~3.1 games. Their issues were in the Championship where they had two 50:50 games with Donegal but won neither and then lost as 1/12 favourites at home to Longford. That loss alone equates to -0.893 Expt Wins.

Versus the handicap

Team Games played Games covered Cover % Cover Rank Win % rank Expt Wins rank
Laois 12 4 33.3% =28 =24 =23
Derry 12 4 33.3% =28 17 25
Waterford 9 3 33.3% =28 28 27
Down 9 3 33.3% =28 32 31
Wicklow 9 2 22.2% 32 =24 21

This is the “hope you weren’t relying on these guys throughout the year” listing.

Similar to the positive performers table there is only one team – Down – that appears in the worst list for both Expt Wins and handicap rankings. Again like the top performers those at the bottom of the handicap ranking are also in the bottom third of the Expt Wins ranking.

Waterford & Wicklow appear in the bottom 5 for the second year running. Combining 2015 & 2016 they are running at a 28% cover rate (9 games from 32).

We have already seen one of the teams relegated from Division2 – Armagh – appear in the “worst performing” category so it’s no surprise to see the other two teams that filled out the bottom three of that division make an appearance here. Division2 was seen as ultra-competitive at the start of the year and this was followed through with a high volume of games with a close handicap (see Note4). Once teams started to underperform they were going to struggle against the handicap.


Note1; what is more remarkable, and a cautionary tale re taking trends at face value, is that Kerry were in the bottom two in this metric in 2015. Then they covered in 31% (4 out of 13) of their games. We must always remember that we are dealing with very small sample sizes (and margins) here where a point or two can have a huge effect.

Note2; twenty teams since the start of the 2015 league campaign have started as double digit favourites. Only 7 (35%) have managed to cover this.

Note3; Although the first Laois game was declared null and void it was played as if it was a Championship game and we have odds & a result for it so it is included overall.

Note4; 86% (25 games out of 29) had a handicap of 2 or less in Division2. This was 52% for Division1, 83% for Division3 and 48% for Division4

Thinking out loud; In GAA betting the handicap is intrinsically linked to the match price. If those with high Expt Wins (essentially odds on shots) generally cover at a better rate, and the corollary is true for those with low Expt Wins are the linkages between match price and handicap line “out”?