Why follow the evolution of betting odds?

Definition

Monitoring the evolution of odds is essential. But before we dive into it, what even are odds?

Odds are the multiplier applied to your bet to calculate potential winnings. The higher the odds, the greater the potential winnings. Therefore, it represents the probability of a given event, such as a tennis player's victory or the score of a football match. For example, if Djokovic's odds of winning are 2, simply take the inverse (1 divided by 2 = 0.5, so in this instance 50%) to get the probability. Simple, isn't it? Not quite…

There are a few key distinctions to understand between odds and probability.

If you skip them, you risk (very) badly evaluating the relevance of your bet.

To avoid this, you have to understand how odds are established by the bookmaker. I’ll try to keep this broad as each bookmaker works differently.

In general, therefore, a bookmaker subcontracts the odds it displays on its site to a specialised company armed with engineers. The two best-known companies in this field are BetRadar and BetGenius. Not only do they provide the odds, but they also establish the parameters that govern the fluctuation of the latter.

Once the odds are available, the bookmaker can make any adjustments they wish, depending on:

👉 the attractiveness of the bet (number of bettors and volume of bets also called liquidity)

👉 the margin one hopes to have

👉 the psychological biases of punters

👉 its marketing policy on this match or particular bet

And that, unless you work directly with a bookmaker in a position of responsibility, we cannot know. It is therefore appropriate to use what is called the player return rate, commonly known as the PRR, as an indicator.

The PRR is defined as the proportion of the sums won by the player(s) in relation to their total wager(s) or expenditure. It is therefore a question of the mass of money which does not return to the operator or to the public authorities - but to the players instead.

For example, as I write this article, Medvedev is meeting Tsitsipas in the semi-finals of the Rome 2023 tournament. The odds for victory are 2.25 and 1.66, giving a PRR of 1/(1/2.25+1 /1.66) = 95.5%. This means that on average, if this same match is played 1 million times with new bettors each time, 95.5% of the stakes will be returned to them. This must therefore serve as an indicator of the amount that the % of stakes that the bookmaker is ready to make on this match or on this bet. If it is high (i.e. close to 100%), then it potentially returns a lot of bets and the inverse of an odds can potentially more accurately represent the probability of the outcome of the event in question.

All that is to say that when you take the inverse of an odds, you have a probability within a margin whose size we can feel thanks to the TRJ. But as all that is a little vague, we prefer to do the opposite, that is to say calculate a probability ourselves (I estimate for example that Medvedev has a 45% chance of beating Tsitsipas) and transform it into odds (1/0.45=2.22 for Medvedev, and 1/0.55=1.82 for Tsitsipas). I believe here that there is subsequently no betting opportunity…

Odds evolution

Odds change constantly before and during a sporting event. Bookmakers adjust odds based on information they receive, money entering the betting market, and team or player performance.

If you are a bettor, you ought to monitor the odds to identify advantageous betting opportunities. For example, if a team is initially considered the underdog but their odds start to drop, this may indicate that the bookmakers have received information about an injury or a change that increases that team's chances of winning. You can then decide to bet on this team before the odds drop even further.

Moreover, you can use the evolution of the odds to determine if the bookmakers have underestimated or overestimated the chances of a team or a player. If a player is considered the favourite, but his odds start to drop, it may indicate that the bookmakers have overestimated his odds. Bettors can then decide to bet on the underdog for bigger payouts.

In summary, following the evolution of the odds is essential for you if you are a bettor. This allows you to identify advantageous opportunities and determine whether the bookmakers have underestimated or overestimated a team or player's chances. It is for this reason that we provide in our mobile app a real-time odds evolution graph (updated every 10 minutes) as well as a betting trend indicator taken by bettors around the world.

In my example, if during his lifetime Medvedev's odds go through 2.40, I have a betting opportunity at that exact moment. It’s the same during a live game, but you have to be more responsive. There, for example, the match was interrupted by rain at 4-4 in the 1st set, and Medvedev's odds rose to 2.35 even though (in my view) the Russian has more chances of winning on heavy ground because that favors his defending game and slightly decreases the importance of service while Tsitsipas serves excellently in this tournament …

So what should I do? Go for it?