# European Sports Books Release Olympic Swimming Odds

##### by Andrew Mering 12

August 03rd, 2016

The odds in this article are provided for entertainment purposes only. If you have strong opinions about who’s going to win, the SwimSwam pick ’em contest is for you.

The Olympics are the biggest sporting event of 2016, so, of course, it’s possible to gamble on them. The swimming betting scene is small, but it does exist. As a swim fan the best part of shady Olympic gambling is that betting odds are essentially a dispassionate prediction of the results. A sportsbook’s only incentives are to make money, and the best way to do that is to estimate the probabilities of different outcomes as closely as possible.

The most robust odds available are on who wins gold in each event. There are betting markets on top 3 finishes, but there’s almost no active betting so their top 3 odds are useless. The betting markets on gold medalists are a bit better. There are up to several thousand dollars on the most contentious events, but most events have less than $500 at risk. That’s generally not enough for the market to settle on a trust worth prediction. Gold medal odds are fairly consistent across the sports books I checked, so I grabbed all the odds from one (specifically SkyBet) instead of doing a compilation stat . So I’m clear: in betting markets you bet against other another person. Market forces decide the predicted odds. Sports books are essentially a casino. I’m using the odds offered by the sports books. ### Basic Takeaways: • The biggest toss up in the relays is women’s medley relay with Australia at 8/11 and the USA at 11/8, and the men’s 4X100 free with France at 5/4, Australia at 7/4, and the USA at 3/1. • The other relay’s aren’t expected to be that competitive. The next worst winner’s odds are the US men in the 4X200 at 2/7. • Katie Ledecky is the meet’s biggest favorite at 1/100 in the 400 and 800 free’s. Next best is Katinka Hosszu in the 200 IM and the Australian women’s 4X100, both at 1/33. Adam Peaty in the 100 breast at 1/6 is the strongest men’s favorite. • The biggest individual tossups outside of the open water (where the best odds are 4/1) is the women’s 200 fly. The best odds there belong to Mireira Belmonte and Natsumi Hoshi at 5/2. Close behind are Franziska Hentke at 4/1 and Madeline Groves at 9/2. The biggest men’s tossup is the 200 breast with both Marco Koch and Jacob Pebley at 13/8. • The top 8 implied gold medal counts (from the corrected probabilities below) are USA: 8.9, Australia: 7.0, Hungary: 2.6, Japan: 2.3, China: 2.1, Great Britain: 1.6, Sweden 1.3, France 1.2 ### More Complicated Takeaways: The USA’s 3/1 odds to with the men’s 4X100 free relay implies a 25% chance that they win. (bet$1 at 3/1, 75% of the time you lose $1, 25% of the time you win$3. So it’s break even. That is .75*-1+.25*3=0). However, 25% is not the sports books real opinion of the USA’s chances to win that relay.

Sports books don’t offer their true odds to players, otherwise they would only break even in the long term (and the only way to make money is to fix the outcome). Instead they build in an adjustment called vigorish. Most of the time this adjustment is relatively small. For example, a standard bet on an over/under  is offered at 10/11 for both the over and under. This means players are required to risk $11 to win$10. In the long run, a bet at 10/11 breaks even if the event in question happens 52.4% of the time. This means that 52.4% is the probability of the event implied by the offered odds, but the book actually thinks it will happen 50% of the time. We can correct for the vigorish by adding up all the implied probabilities of all possible bets and dividing by the sum. On a standard over/under bet the book offers 10/11 on the over and 10/11 on the under. That gives 52.4%+52.4%=104.8%. 52.4%/104.8%=50%, the book’s actual probability of either the over or the under.

To correct for the vigorish in the example above we needed to divided the implied probabilities by 1.04. In the odds being given by the books for the Olympics, the correction factor is 1.3.  A number that high can imply a any of couple things. 1. The books don’t have a ton of faith in their projection, so they built in a huge margin of error to cover their back against someone with a better projection. 2. The books think that only idiots are betting on swimming at the Olympics, so they’re giving bettors terrible value to make more money.

My advice: Do not bet on these lines. There is such a large margin of error built in that it’s almost impossible to find a value bet. (also gambling is illegal in most US states, so, for many, there’s extra incentive not to throw money away)

The table below contains the betting odds, the probability implied by those odds and the probability corrected for the vigorish (aka the book’s actual guess of what will happen). One note on the corrected probabilities. I don’t know how the books actually applied the viogrish. I simply divided by the summed probability. This runs into problems with high probability events. For example, an overround of 30% on a true probability of 80% would give number over 100%  (1.3*.8=1.04). Obviously that’s non nonsensical. There is some evidence that the books corrected for this with a smaller vigorish in events with high probability winners. In most events the implied probabilities sum to almost exactly 130%. In the women’s 400 free, where Katie Ledecky is a huge favorite, the implied probabilities sum to only 125%. Similarly, in the open water, the biggest toss up, the implied probabilities summed to 140%.

It’s also possible they used a sliding formula that applied adjustments unevenly. If that’s the case, it’s not corrected for below. View the corrected probabilities in any events with a big favorite with suspicion.

The full sportsbook odds on gold medal winners. Implied probability is the probability if we take the sports book’s odds at face value (what true probability makes those odds break even). Corrected probability is the implied probability corrected for the vigorish. (I excluded all swimmers with an implied probability below 1%):

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Rajon
5 years ago

Hit me up for some real action. Taking everything from fencing to ping pong

Joe
5 years ago

Were I a betting man (with, say, $100), here are some lines I’d think about. I don’t think of all of these picks as favorites in my mind (except Phelps in the 200 IM and the USA men 400 free relay who I think are going to show up to perform).$10 Murphy 200 back at 9/2
$5 VdB 100 breast at 7/2$10 Gyurta 200 breast at 6/1 and $10 Cordes 200 breast at 8/1$11 Phelps 200 IM at 10/11
$19 USA men 400 free relay at 3/1$10 Pellegrini 200 free at 5/1
$5 Worrell 100 fly at 16/1 and$10 Vollmer 100 fly at 18/1

I’ll check back after… Read more »

completelyconquered
5 years ago

I do not think I will take the VdB bet in the 100 breast. Peaty is a lock for me. I like the Murphy 200 back, USA Men 4×100 free relay, and the Cordes 200 breast bets.

completelyconquered
5 years ago

And, DiRado in the 400 IM at 10 to 1.

Joe
5 years ago

Checking back in – I did pretty nice. $10 on Murphy at 9/2 wins me$45, $11 on Phelps at 10/11 wins me$10, and $19 on USA men 400 free relay wins me$57. So that’s a return of $40 from my initial bet and$112 on the winnings for a total of $152. Not bad. marley09 5 years ago We need betting lines for 8 to 12 year olds to pass the time during those long 4 day winter swim meets. NeverWas 5 years ago I’ll put a$100 on Townley Hass in the 200 with 22-1.

Sun Yang at 11/10 is ridiculous. 3/1 he’s a no show for the final. Could it happen twice?

King in da norf
5 years ago

In women 200 fly, Madeline Groves at 18% while Cammile Adams is only at 4%.

Commonwombat is going to love this 🙂

jcinho
5 years ago

The fixed odds bookies get their odds these days from the betting exchanges (Betfair is the largest, probably not available in the US) and until enough money has been exchanged (matched), then the odds are pretty meaningless. Expect the exchanges to increased their volumes matched after the prelims as punters see the form of the swimmers. A company like Skybet will have a huge markup (if you add up all of the odds of backing any “realistic” winner, the figure will be well below 90%. The difference between that figure and 100% is their profit margin), so you’ll get fairer odds from the exchanges when the money starts to flow on them.

jcinho