July - When a Fan's Thoughts Turn to Tanking

Most major Australian sports have their iconic annual event. Cricket has its Boxing Day test, tennis and golf have their respective Australian Opens, rugby league has the State of Origin series, rugby union the Bledisloe, and AFL, it now seems, has the Tanking Debate, usually commencing near Round 15 or 16 and running to the end of the season proper.

The T-word has been all over the Melbourne newspapers and various footy websites this week, perhaps most startlingly in the form of Terry Wallace's admission that in Round 22 of 2007 in the Tigers clash against St Kilda, a game in which the Tigers led by 3 points at the final change but went on to lose by 10 points:

"while he had not "tanked" during the Trent Cotchin game in Round 22, 2007, he had let the contest run its natural course without intervention"

That stain on the competition's reputation (coupled, I'll admit, with he realisation that the loss cost MAFL Investors an additional return of about 13% for that year) makes it all the more apparent to me that the draft system, especially the priority draft component, must change.

Here's what I wrote on the topic - presciently as it turns out - in the newsletter for Round 19 of 2007.

Tanking and the Draft

If you’re a diehard AFL fan and completely conversant with the nuances of the Draft, please feel free to skip this next section of the newsletter.

I thought that a number of you might be interested to know why, in some quarters, there’s such a fuss around this time of year about “The Draft” and its potential impact on the commitment levels of teams towards the bottom of the ladder.

The Draft is, as Wikipedia puts it, the “annual draft of young talent” into the AFL that takes place prior to the start of each season. In the words of the AFL’s own website:

"In simple terms, the NAB AFL Draft is designed to give clubs which finished lower on the ladder the first opportunity to pick the best new talent in Australia. At season's end, all clubs are allocated draft selections. The club that finished last receives the first selection, the second last team gets the second selection and so on until the premier receives the 16th selection."

So, here’s the first issue: towards season’s end, those teams for whom all hopes of a Finals berth have long since left the stadium find that there’s more to be gained by losing games than there is by winning them.

Why? Well say, for example, that Richmond suddenly remembered what the big sticks are there for and jagged two wins in the last four games, leaping a startled Melbourne in the process, relegating them to position Spoon. The Tigers’ reward for such a stunning effort would be to (possibly – see below) hand Melbourne the sweetest of draft plums, the Number 1 draft pick, while relegating themselves to the Number 2 pick. Now, in truth, over the years, Number 1 picks have not always worked out better than Number 2 picks, but think about it this way: isn’t it always nicer to have first hand into the Quality Assortment?

Now entereth the notion of Priority Picks, which accrue to those teams who have demonstrated season-long ineptitude to the extent that they’ve accumulated fewer than 17 points over its duration. They get a second draft pick prior to everyone else’s second draft pick and then a third pick not that long after, once all the other Priority Picks have taken place. So, for example, if a team comes last and wins, say, four games, it gets Pick #1, Pick #17 (their Priority pick, immediately after all the remaining teams have had their first pick) and then Pick #18 (their true second round Pick). If more than one team is in entitled to Priority Picks then the Picks are taken in reverse ladder order.

Still with me?

Now, the final twist. If a team has proven its footballing inadequacy knows not the bounds of a single year, having done so by securing fewer than 17 points in each of two successive seasons, then it gets its Priority Pick before anyone else gets even their first round pick. Once again, if more than one team is in this situation, then the tips are taken in reverse ladder order.

So, what’s the relevance to this year? Well, last year Carlton managed only 14 points and this year they’re perched precipitously on 16 points. If they lose their next four games, their first three draft picks will be #1 (their Priority Pick), #4 (their first round pick), and #20 (their second round pick); if they win or even draw one or more of their remaining games and do this without leaping a ladder spot, their first three draft picks will be #3, #19 and #35. Which would you prefer?

I find it hard to believe that a professional footballer or coach could ever succumb to the temptation to “tank” games (as it’s called), but the game’s administrators should never have set up the draft process in such a way that it incites such speculation every year around this time.

I can think of a couple of ways of preserving the intent of the current draft process without so blatantly rewarding failure and inviting suspicion and rumour. We’ll talk about this some more next week.

*****

In the following week's newsletter, I wrote this:

Revising the Draft

With the Tigers and the Dees winning last week, I guess many would feel that the “tanking” issue has been cast aside for yet another season. Up to a point, that’s probably a fair assessment, although only a win by the Blues could truly muffle all the critics.

Regardless, as I said last week, it’s unfair to leave any of the teams in a position where they could even be suspected of putting in anything other than a 100% effort.

I have two suggestions for changes to the draft that would broadly preserve its intent but that would also go a long way to removing much of the contention that currently exists.

(1) Randomise the draft to some extent. Sure, give teams further down the ladder a strong chance of getting early draft picks, but don’t make ladder position completely determine the pick order. One way to achieve this would be to place balls in an urn with the number of balls increasing as ladder position increased. So, for example, the team that finished 9th might get 5 balls in the urn; 10th might get 6 balls, and so on. Then, draw from this urn to determine the order of draft picks.

Actually, although it’s not strictly in keeping with the current spirit of the draft, I’d like to see this system used in such a way that marginally more balls are placed in the urn for teams higher up the ladder to ensure that all teams are still striving for victory all the way to Round 22.

(2) Base draft picks on ladder position at the end of Round 11, not Round 22.

Sides that are poor performers generally don’t need 22 rounds to prove it; 11 rounds should be more than enough. What’s more, I reckon that it’s far less likely that a team would even consider tanking say rounds 9, 10 and 11 when there’s still so much of the season to go that a spot in the Finals is not totally out of the question. With this approach I’d be happy to stick with the current notion that 1st draft pick accrues to the team at the foot at the ladder.

Under either of these new draft regimes, the notion of Priority Picks has to go. Let’s compensate for underperformance but not lavish it with silken opportunity.

****

My opinion hasn't changed. The changes to the draft for the next few years that have been made to smooth the entry of the Gold Coast into the competition probably mean that we're stuck with a version of the draft we have now for the next few years. After that though, we do have to fix it because it is broken.

The Differential Difference

Though there are numerous differences between the various football codes in Australia, two that have always struck me as arbitrary are AFL's awarding of 4 points for a victory and 2 from a draw (why not, say, pi and pi/2 if you just want to be different?) and AFL's use of percentage rather than points differential to separate teams that are level on competition points.

I'd long suspected that this latter choice would only rarely be significant - that is, that a team with a superior percentage would not also enjoy a superior points differential - and thought it time to let the data speak for itself.

Sure enough, a review of the final competition ladders for all 112 seasons, 1897 to 2008, shows that the AFL's choice of tiebreaker has mattered only 8 times and that on only 3 of those occasions (shown in grey below) has it had any bearing on the conduct of the finals.

Historically, Richmond has been the greatest beneficiary of the AFL's choice of tiebreaker, being awarded the higher ladder position on the basis of percentage on 3 occasions when the use of points differential would have meant otherwise. Essendon and St Kilda have suffered most from the use of percentage, being consigned to a lower ladder position on 2 occasions each.

There you go: trivia that even a trivia buff would dismiss as trivial.

Who'll Be There in September (Maybe)?

With just 6 rounds to go in the competition, a few articles are emerging about how the teams will fare over the remainder of the season and, most importantly, who'll finish where in the top 8.

Using the MARS Ratings from MAFL Stats I've also predicted the results for the remainder of the season, details of which appear below:



On the right of the table I've provided the game-by-game projections for each team. Green boxes denote victories, red losses, and a bracketed "H", "A" or "N" denote Home, Away and Neutral Ground venues respectively.

If these projections are accurate, there's not a lot of change that we'll see amongst the top 8. In fact, we'll see no change at all in terms of its membership and only a couple of significant changes in terms of its ordering.

Carlton, I'm forecasting, will leap 3 places and secure a top 4 spot, beating Collingwood (currently 4th), the Roos (12th), Port (9th), Melbourne (15th), and Adelaide (6th) in so doing, losing only to the 2nd-placed Geelong in Round 19. This string of results will draw Carlton level with the Lions on 56 points, but will see them grab 4th with a superior percentage.

Collingwood will surrender their top 4 spot, dropping to 6th due to losses to Carlton (7th), Adelaide (6th), and the Dogs (3rd). Victories over the Lions (5th), Richmond (14th), and Sydney (11th) won't be enough.

Port Adelaide and Hawthorn are projected to finish level with the Dons on 44 points but will miss a spot in the eight on percentages, in Hawthorn's case despite finishing the season with a three-game winning streak.

The Decline of the Humble Behind

Last year, you might recall, a spate of deliberately rushed behinds prompted the AFL to review and ultimately change the laws relating to this form of scoring.

Has the change led to a reduction in the number of behinds recorded in each game? The evidence is fairly strong:

So far this season we've seen 22.3 behinds per game, which is 2.6 per game fewer than we saw in 2008 and puts us on track to record the lowest number of average behinds per game since 1915. Back then though goals came as much more of a surprise, so a spectator at an average game in 1915 could expect to witness only 16 goals to go along with the 22 behinds. Happy days.

This year's behind decline continues a trend during which the number of behinds per game has dropped from a high of 27.3 per game in 1991 to its current level, a full 5 behinds fewer, interrupted only by occasional upticks such as the 25.1 behinds per game recorded in 2007 and the 24.9 recorded in 2008.

While behind numbers have been falling recently, goals per game have also trended down - from 29.6 in 1991, to this season's current average of 26.8. Still, AFL followers can expect to witness more goals than behinds in most games they watch. This wasn't always the case. Not until the season of 1969 had there been a single season with more goals than behinds, and not until 1976 did such an outcome became a regular occurrence. In only one season since then, 1981, have fans endured more behinds than goals across the entire season.

On a game-by-game basis, 90 of 128 games this season, or a smidge over 70%, have produced more goals than behinds. Four more games have produced an equal number of each.

As a logical consequence of all these trends, behinds have had a significantly smaller impact on the result of games, as evidenced by the chart below which shows the percentage of scoring attributable to behinds falling from above 20% in the very early seasons to around 15% across the period 1930 to 1980, to this season's 12.2%, the second-lowest percentage of all time, surpassed only by the 11.9% of season 2000.

(There are more statistical analyses of the AFL on MAFL Online's sister site at MAFL Stats.)

Does The Favourite Have It Covered?

You've wagered on Geelong - a line bet in which you've given 46.5 points start - and they lead by 42 points at three-quarter time. What price should you accept from someone wanting to purchase your wager? They also led by 44 points at quarter time and 43 points at half time. What prices should you have accepted then?

In this blog I've analysed line betting results since 2006 and derived three models to answer questions similar the one above. These models take as inputs the handicap offered by the favourite and the favourite's margin relative to that handicap at a particular quarter break. The output they provide is the probability that the favourite will go on to cover the spread given the situation they find themselves in at the end of some quarter.

The chart below plots these probabilities against margins relative to the spread at quarter time for 8 different handicap levels.

Negative margins mean that the favourite has already covered the spread, positive margins that there's still some spread to be covered.

The top line tracks the probability that a 47.5 point favourite covers the spread given different margins relative to the spread at quarter time. So, for example, if the favourite has the spread covered by 5.5 points (ie leads by 53 points) at quarter time, there's a 90% chance that the favourite will go on to cover the spread at full time.

In comparison, the bottom line tracks the probability that a 6.5 point favourite covers the spread given different margins relative to the spread at quarter time. If a favourite such as this has the spread covered by 5.5 points (ie leads by 12 points) at quarter time, there's only a 60% chance that this team will go on to cover the spread at full time. The logic of this is that a 6.5 point favourite is, relatively, less strong than a 47.5 point favourite and so more liable to fail to cover the spread for any given margin relative to the spread at quarter time.

Another way to look at this same data is to create a table showing what margin relative to the spread is required for an X-point favourite to have a given probability of covering the spread.

So, for example, for the chances of covering the spread to be even, a 6.5 point favourite can afford to lead by only 4 or 5 (ie be 2 points short of covering) at quarter time and a 47.5 point favourite can afford to lead by only 8 or 9 (ie be 39 points short of covering).

The following diagrams provide the same chart and table for the favourite's position at half time.

Finally, these next diagrams provide the same chart and table for the favourite's position at three-quarter time.

I find this last table especially interesting as it shows how fine the difference is at three-quarter time between likely success and possible failure in terms of covering the spread. The difference between a 50% and a 75% probability of covering is only about 9 points and between a 75% and a 90% probability is only 9 points more.

To finish then, let's go back to the question with which I started this blog. A 46.5 point favourite leading by 42 points at three-quarter time is about a 69.4% chance to go on and cover. So, assuming you backed the favourite at $1.90 your expected payout for a 1 unit wager is 0.694 x 0.9 - 0.306 = +0.32 units. So, you'd want to be paid 1.32 units for your wager, given that you also want your original stake back too.

A 46.5 point favourite leading by 44 points at quarter time is about an 85.5% chance to go on and cover, and a similar favourite leading by 43 points at half time is about an 84.7% chance to go on to cover. The expected payouts for these are +0.62 and +0.61 units respectively, so you'd have wanted about 1.62 units to surrender these bets (a little more if you're a risk-taker and a little less if you're risk-averse, but that's a topic for another day ...)

Sometimes, Seven Goals Just Isn't Enough

You might think, if you'd wagers on three teams (albeit outsiders) that led by 8, 7 and 42 points at half time, that at least one of them would take home the biscuits, especially the one that led by 42 points. If you'd thought this over the last weekend, you'd be wrong.

The Dons were the first of the disappointments, leading the Dogs by 8 points at the half only to concede 11 goals in the second half to go down by 33 points. Next came Fremantle, who enjoyed a 7 point buffer at the half and who maintained legitimate hopes until late in the final term only to falter in the wet against the Lions and lose eventually by 15 points.

Then, on Sunday, the Tigers, who led by 7 straight goals (yes, 7) at the half, barely managed to cling on for a draw, which was enough to stop Investors losing a great deal on the game, but wasn't enough to provide them with a profit. In draws, head-to-head wagers pay out at half-price, so teams at prices below $2 pay back less than the amount wagered. Investors had the Tigers at $1.95.

Indeed it was a weekend littered with close finishes for many Investors. The Cats lost on line betting by half a point, Freo won on line betting by two and a half points, and Port won on line betting by a point and a half. Still, most Investors would've swapped those two favourable line betting results for a Tigers head-to-head victory.

In total, New Heritage won 4.5 of 6 wagers and fell 3.3%, Prudence won 4.5 of 7 wagers and fell 4.2%, Hope lost its only bet and fell 5.5%, Chi-squared won 0.5 of 3 wagers and fell a precipitous 33.3%, and Line Redux won 2 of 4 wagers and fell 1%.

As a result, the Recommended Portfolio fell 9.4% to leave it just 4.5% ahead for the season. Other Portfolios fell by between 3.3% and 9.5% to leave them in front for the season by amounts ranging from 7.5% to 35.4%.

On tipping, RYL had the best possible round, landing 7.5 from 8. Silhouette and Shadow bagged 6.5 and 5.5 respectively to jointly lead outright on 93.5 from 128 (73%), 5 tips ahead of BKB on 88.5 from 128 (69%) and a further tip ahead of CTL and STM II on 87.5 from 128 (68%).

Level-stake, home team only, start at Round 6 wagering on the heuristic tipsters has now been profitable for all tipsters except ELO, Chi and HSH. Shadow, Silhouette and STM II are currently up by over 11 units using such a wagering strategy - if only we'd known ...

Chi's and ELO's line betting results were once again poor this weekend, with Chi scoring 3 from 8 and ELO just 2 from 8.

All told, a weekend best forgotten.

Clutch Betting

The English language has many wondrous, often euphonious collective nouns ready to serve as descriptors for sets of objects, especially animals. So we have, for example, an exultation of larks, a murder of crows, a gaggle of geese, a cloud of bats, a flutter of butterflies, a cackle of hyenas, a smack of jellyfish, a deceit of lapwing, a richness of martens, a parliament of owls, a watch of nightingales and - a personal favourite - a prickle of porcupines.

English lacks, however, a collective noun for a group of bets, a deficiency I feel needs to be remedied. Accordingly, I'm nominating the word 'clutch' for this purpose.

Its appropriateness can be argued on a number of fronts.

Firstly, the word clutch evokes images of an anxious punter, betting slips gripped tightly in hand, attention riveted on a large screen that's beaming the performance of some two- or four-legged determiner of his or her fate. Surely such a punter can be said to be in the clutch.

The word's also evocative of the notion of 'clutching at straws', a desperate and generally futile exercise, which can seem an especially apposite metaphor some weekends.

Further and more positively, the term 'clutch' already has a sporting pedigree as an honorific applied to the exalted few who can be expected to perform when it matters - hence 'clutch' putter, 'clutch' hitter, 'clutch' pitcher and, more generally, 'clutch' player.

Clutch it it then.

This weekend Investors most certainly face a clutch of bets, 21 in all for the second weekend in a row, and 8 of them on underdogs priced as high as $3.

Chi-squared's own clutch is the scariest. Three bets totalling over 44% of the Fund, the two largest on Essendon and Fremantle both at $3 and both facing teams that are fighting for top 8 and possible top 4 positions. The remaining bet is on Richmond, also the underdogs, but they're only at $1.95 and the bet is relatively small.

New Heritage is also putting a large proportion of the Fund at risk - just under 63% of the Fund on 6 teams, all of them favourites and all but one of them home teams. The largest wager is just over 13% of the Fund on Geelong at what others might call an unbackable $1.04. The smallest wager is just over 2% on the Roos at $1.80 away to the Tigers.

Prudence, as has been its habit for most of the season, has this week nibbled on a smorgasbord of teams rather than gorging on just a few. It has 7 bets totalling a little over 30% of the Fund, 2 of them on underdogs and including a surprising 2% wager on the Dons at $3. The largest wager is for a trifle under 7% of the Fund on the Cats at $1.04.

Line Redux has four wagers representing 20% of the Fund. Two of these wagers are on favourites (Geelong and Port Adelaide) and the other 2 are on underdogs (Essendon and Fremantle).

(There is still one line market to be posted - that for the Tigers v Roos clash - but I don't expect we'll have a bet in it.)

Hope, whose selectivity has been its hallmark this season, has only 1 bet this week, its 20th of the season and its 6th on the Dons. It has 5.5% of the Fund on them at $3.

Together these bets yield the following Ready Reckoner:

The entire tenor of the weekend will be established late on Friday night for all Investors except MIN#017, though even a Dons win won't make the weekend entirely pot-hole resistant.

Next we move to tipping where we find:

* Essendon are 8-5 favourites over the Dogs. Amongst our top 5 tipsters, Silhouette, BKB and CTL have sided with the Dogs, while Shadow and STM II (along with a cadre of anxious MAFL Investors and a badly-bred Pomeranian) are riding the Don train. Chi could definitely be more convincing in his Dondom - he has them as only 1 point winners making this game one of his two Games of the Round.

* Carlton are unanimous favourites over the suddenly unpopular Swans.

* Geelong are 8-5 favourites over the Dees, the narrowness of their favouritism due mostly to the shortness of the memories of many of our heuristic-based tipsters. Amongst the cream of these tipsters, only Shadow and STM II are lining up behind the Dees in what will surely be the shortest of queues.

* Collingwood are 8-5 favourites over the Hawks. Once again it's only Shadow and STM II from the top 5 tipsters who are supporting the underdogs.

* Brisbane are 11-2 favourites over Fremantle, the sole support for the Dockers coming from HSH and Chi, who has this as his second and final Game of the Round.

* Port Adelaide are unanimous favourites over the Eagles.

* The Roos are 8-5 favourites over Richmond. The Tigers' following amongst our top tipsters is thin: only STM II is in their corner. ELO is another Tigers tipper, though only by 6 points, making this its Game of the Round.

* St Kilda are 11-2 favourites over the Crows, with EI I and II the only ornithologists amongst the MAFL tipsters.

On line betting, ELO will surely improve on its 0 from 8 record last weekend, though I'm not as certain that Chi will better his 3 from 8 performance. This week:

* Chi's on: Essendon, Sydney, Melbourne, Collingwood, Fremantle, West Coast, Richmond and Adelaide.

* ELO's on: Essendon, Sydney, Geelong, Collingwood, Brisbane Lions, West Coast, Richmond and St Kilda.

On Line Betting this year teams receiving start have fared much better than those giving it. The current tally is 69-51 in favour of the teams receiving start. The teams with the best records when receiving start are Carlton (4-0), St Kilda (3-0), Brisbane (4-1), and West Coast (8-3). Those with the poorest records when giving start are Fremantle (0-4), West Coast (0-4), Hawthorn (1-11), Port Adelaide (3-6), Adelaide (2-4), Sydney (2-4), Geelong (6-9) and Carlton (4-7).

One last statistic before I go. Which teams do you think have the best and worst win-loss records this year in games that have been decided by fewer than 12 points?

Three teams have perfect records: Essendon (2-0), St Kilda (2-0) and Adelaide (1-0). The Hawks (3-1) also have a strongly positive record. The worst, or perhaps the unluckiest, team in these situations has been Carlton (1-4), followed by 5 teams - Collingwood, Port Adelaide, Richmond, West Coast and the Western Bulldogs - all with 1-2 records.

No team has failed to register at least one result where the margin of victory or defeat has been 11 points or fewer.