# Most Common Bookie Mistakes

In a previous article, we discussed the most common mistakes made by bettors when betting on sports. While novice punters are most vulnerable to such errors, both intermediate and veteran punters are still susceptible to making a habit of both poor discipline, reckless wagering and neglecting the fundamentals of successful betting.

Inaccurate Odds – Derivative Markets – Arbitrage Opportunities – Value Accumulators

But while it’s common for punters to make errors when betting on sports, you might be surprised to learn that bookmakers are likewise prone to errors or at the very least, provide punters with opportunities to enhance their betting returns.

In this article, we will discuss the most common errors made by bookmakers and the ways in which bettors such as yourself can take advantage.

## Inaccurate Odds

**Bookmakers can make mistakes when setting the odds**

So let’s begin with the most obvious. While bookmakers employ some of the sharpest sports betting minds and analytical tools available in the service of setting the odds for thousands of betting markets each day, they still make errors and do so repeatedly. While the days of the market trader or odds compiler are long gone, replaced by algorithms and automated market management, bookmakers still make mistakes when it comes to setting the odds.

In fact, some may say that it is due to this automation and heavy reliance on algorithms that make bookmakers even more vulnerable to the shrewd punter. While a data reliant algorithm may give a given football club a certain probability of winning an upcoming match, a punter in possession of a far more intimate knowledge of that team and the league that they compete in, will be able to recognise any error and exploit it to their advantage.

Identifying erroneous odds and taking advantage is typically known as “value betting”, and it is this value betting that is the foundation of any profitable betting strategy. If you are not identifying value odds I.e odds that incorrectly reflect the true probabilities of a given outcome occurring, you are not going to be making money long term as a sports bettor. If you do not maintain betting discipline and bet only when you have identified value betting opportunities, you will only lose money. It’s as simple as that.

Value identification is essentially determining that a given outcome is more likely to happen than what the bookmaker odds would suggest.

So for example, if you believe there is a 65% chance that a football match will end with over 2.5 goals scored, and the bookmaker odds suggest a 50% chance, you have identified what you believe to be a value betting opportunity.

Using decimal odds, a value bet is calculated in the following manner.

Let’s say we are betting on an upcoming football match between Liverpool and Chelsea. Liverpool are at odds of 4.50 to win the match. We conduct our research, crunch our numbers and determine that the chances of Liverpool winning is 30%.

Is betting on Liverpool a value bet?

To find out we simply multiply Liverpool’s odds by 30%.

*value = decimal odds x chance of outcome occurring*

**4.50 x 0.30 = 1.35**

If the answer is above 1, then we have a value bet. The value can be calculated simply by subtracting 1, to give us in this example, 0.35, or in other words, a 35% value bet.

On the other hand, if the answer is below 1, there is no value and we should not place a bet.

*Identifying Incorrect Odds*

*Identifying Incorrect Odds*

That all sounds very inspiring but how do we know we have identified a true value betting opportunity?

While maintaining discipline and placing bets only when you have identified value is the theoretical foundation of all successful betting, without developing an eye for true betting value, you will again only lose money. Regardless of how disciplined you remain, unless your value bets are indeed offering true value, you will not last long as a serious sports bettor.

There are a number of ways to identify betting value. But whichever way you slice it, what differentiates a profitable bettor from an unprofitable bettor is knowledge and experience.

In order to continually make money betting on sports, a successful bettor must possess a more intimate knowledge of a given sports betting market than the bookmaker.

This is where specialisation is key. If you want to take advantage of bookmaker errors, you must focus on a limited range of markets, becoming so familiar with these markets and their dynamics that value identification almost becomes second nature.

In this respect, many bettors focus on secondary markets as a means of identifying value, concluding that given a number of resources devoted to primary markets such as 1X2 and Asian handicap in major football leagues of Europe such as the Premier League and Champions League, there is more likelihood of finding value in secondary markets in more obscure leagues.

For example betting on second division leagues around Europe focusing only on Both Teams To Score markets or First Half Goal Totals etc. In short, if you want to find value, you have to look where bookmakers are more vulnerable to errors, where the value is more likely to be found and this is typically in less popular leagues, competitions and betting markets.

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*Added Difficulty*

*Added Difficulty*

Whichever way you look at it, identifying bookmaker errors especially when it comes to their odds, is both the toughest and most essential task of sports betting. The task is made even more difficult by the fact that bookmakers do not offer full value odds, taking a slice of the odds known as the margin.

We will not go into too much detail now other than to offer a brief but instructive example. Let’s say we want to bet on coin tosses. We are offered the following odds:

**Heads 1.90**

**Tails 1.90**

The likelihood of each outcome is 50%, but the odds on offer are not full value. If they were full value each of heads or tails would be at odds of 2.00.

So in this example, to make money betting on heads, we would have to have an overall strike rate of 52.7% just to make the slightest of profits.

**I.e 0.527 x 1.90 = 1.0013**

But as we can only expect to hit 50% of our bets on heads over the long term, we will ultimately lose money.

Bookmakers employ a margin to protect themselves from erroneous betting odds being exploited by cunning bettors. This is why you will see bookmakers impose higher margins on the markets they feel most vulnerable to as well as offering lower bet limits.

For example, a bookmaker may offer odds of 1.95 on Asian handicaps for Premier League matches but only odds of 1.90 for Asian handicaps for English National League matches. Yes, the margin makes it difficult to take advantage of incorrect betting odds, but many bettors continue to make money betting on obscure markets, taking advantage of less vigilant bookmakers.

Another issue is what is known as the “palpable error”, also known as a “palp”. What is a palpable error?

A palpable error is when a bookmaker determines after a market has been settled that the odds they offered were clearly an error and that all winning bets will be voided. This is obviously a contentious issue with many punters crying foul when their winning bets are voided especially when bookmakers do not refund losing bets placed at the listed odds.

While bookmaker terms and conditions may clearly set the rules when it comes to palpable errors, many bettors feel that it is the responsibility of the bookmaker to list their odds accurately. Either way, the palpable error rule is another concern to take into account when assessing bookmaker odds.

## Derivative Markets

**Betting markets are linked to each other, use it!**

Another error bookmakers make is in offering derivative markets. What is a derivative market? Well, it means that within a given sporting event, odds for one outcome are often correlated with the odds for another outcome within that same given event.

Let’s consider a familiar example. Within a given football match the odds for the 1X2 market is typically correlated with the odds for the Asian handicap markets. For example, let’s say that Arsenal are hosting Tottenham in an upcoming Premier League match.

The odds for the 1X2 market are as follows:

**Arsenal 2.10**

**Draw 3.50**

**Tottenham 4.20**

The odds for the Asian handicap markets are as follows:

**Arsenal -0.5, 2.10**

**Tottenham +0.5, 1.91**

This is a simple example but serves to show how two seemingly discrete betting markets are correlated. The odds of Arsenal winning the match are 2.10, with their odds of covering the -0.5 goal handicap the very same odds of 2.10, while the odds of either the match ending in a draw or a Tottenham victory combine for the same odds as Tottenham covering the +0.5 handicap, those odds being 1.91.

*Exploiting These Markets*

*Exploiting These Markets*

Taking advantage of these markets is a difficult task but one that can be quite profitable. Major bookmakers now offer literally in excess of a hundred betting markets for major football league matches, particularly the major leagues of Europe. The majority of these markets are created from goal expectation models. A goal expectation model determines the likely number of goals to be scored based on performance data for each club. For example, the goal expectation model for an upcoming match may be:

**Everton 1.15 goals**

**Newcastle 1.05 goals**

**Total Goals 2.20 goals**

From this basic projection, the odds for dozens of betting markets will be calculated including not only match results and handicaps but likewise goal totals, both teams to score, draw no bet and so on.

So how can we exploit these markets? The fundamental task is in finding inconsistencies and conflicts between two or more given markets and then wagering on both so as to create a value betting opportunity. For example, some bettors look for inconsistencies between Over/Under 2.5 goals and Both Teams To Score markets, looking for instances where for example the odds on Over 2.5 goals and BTTS score No are both excesses of 2.00.

It should be stated that you will not find opportunities for surebets (which we will discuss shortly) when looking to take advantage of correlated markets.

What you can find however are tendencies that the markets do not take into account.

For example, a shrewd football bettor may notice that certain teams have a tendency to surge in the second half, while others are prone to fall away. These are just two simple observations but are subjective elements that bookmaker odds generally will not take into account. Observing team tendencies coupled with data analysis can help you find true betting value in more obscure markets.

Let’s say you have observed that Manchester United generally start slowly at home and have done so since their current manager arrived two seasons ago. Let’s further say that West Ham have shown the tendency to come out fast when travelling away.

If we identify such a combination, then betting on West Ham to either win the 1st half or to win the 1st half handicap would be a great value bet given that the odds for either market would merely reflect the chances of both sides winning the match fulltime and not take into account the tendencies of either side in the opening half of the match.

While such value opportunities can be found, bookmakers will again protect themselves with higher margins on derivative markets such as these. Regardless, there is still plenty of value to be found and analysing derivative markets for value opportunities is well worth your time.

*Go In Play*

*Go In Play*

Live betting offers bettors a greater number of derivative markets to take advantage of. There’s a reason why bookmakers resisted the inception of live betting and if it weren’t for the explosion in popularity of in play betting and trading on betting exchanges such as Betfair, bookmakers simply would never have offered live betting.

Why? Because just like derivative markets, live betting markets are open to exploitation by savvy bettors.

While the early days of live betting saw bookmakers offer a limited number of in play markets on even the most popular leagues and tournaments, bettors can now bet on literally dozens of in play markets. This presents bettors with a great number of opportunities to find value bets.

For example, let’s say that Chelsea are hosting Crystal Palace and have taken a 3-0 in the 65th minute. Your analysis has determined that Crystal Palace have a tendency to collapse away from home when down multiple goals. You place a bet on the match finishing over 4.5 goals. In the remaining 25 minutes, Chelsea score twice with the match finish 5-0 in their favour.

Again, live betting odds are calculated based on pre-match goal expectations for each club, the current score and the time remaining in the match. They will not take into account subjective tendencies of the competing teams.

## Arbitrage Opportunities

**The most important thing in the arbitrage bets is the balance.**

Whatever you want to call them, arbitrage opportunities are another error to take advantage of.

What is an arbitrage opportunity? An arbitrage bet (also known as ‘surebets’ or ‘arbs’) is a combination of bets that ensures a profit no matter what the outcome. Sure, it sounds too good to be true, but there are numerous arbitrage opportunities to be found every day of the week.

How can you find an arbitrage bet? An arb simply involves finding two bookmakers offering conflicting odds on an outcome in a single sports betting event. Let’s consider the following example:

**Over/Under 2.5 goals**

**Bookmaker A offering odds of 2.10, Over 2.5 goals**

**Bookmaker B offering odds of 2.05, Under 2.5 goals**

As we can see from the example above, no matter what outcome we bet on, either Over 2.5 goals or Under 2.5 goals, we will make a profit. This is an arbitrage opportunity.

While most arbitrage opportunities are marginal in value, there are occasions where bookmakers are slow to react to breaking news, leaving themselves open to bettors ready and willing to take advantage of such bookmaker errors.

Let’s consider an example. Manchester City are odds of 3.00 to win an upcoming Premier League match. They are expected to rest a number of players for a midweek European fixture. In the lead up to the match, it turns out that they will play a full-strength squad. On hearing the news, the average odds for Manchester City to win shorten to 2.50. While most bookmakers slice their odds, one bookmaker is late to move leaving their odds at 3.00 and vulnerable to an arbitrage wager.

Now, in reality, it’s unlikely to find an arbitrage opportunity in markets relating to a major sporting event. Arbitrage opportunities are more likely to be found on more obscure betting events, such as lower league football, regional tennis tournaments, national basketball and hockey leagues. For example, the news of a key striker ruled out of an upcoming Austrian second division match is more likely to provide an arbitrage opportunity than news of a Premier League player set to miss.

Another market to exploit are both Group Winner and Group Qualifier markets for Champions League, Europa League as well as World Cup and Euro tournaments. This is especially true when markets are first listed. You will very often find surebet opportunities across a range of bookmakers until these markets settle which can take days.

*Finding A Surebet*

*Finding A Surebet*

So how can we spot a surebet? Well spotting a surebet such as these takes a little bit of math.

When it comes to exploiting an arbitrage opportunity there are two questions we need to consider.

The first, how do we know that we have a surebet available and second, how much should you bet so as to claim your risk-free profit?

Identifying an arbitrage opportunity involves calculating and adding the implied probabilities of the best odds available for each outcome of the market you want to bet on. Fortunately calculating the implied probability is simple. All you need to do is divide the decimal odds by 1. Really, that’s it.

Let’s consider an upcoming Champions League match between Barcelona and Bayern Munich. The best odds available for the Over/Under 2.5 goals markets are as follows:

Bookmaker A, Over 2.5 goals, 2.10

Bookmaker B, Under 2.5 goals, 2.05

Bookmaker A, Over 2.5 goals, 2.10

Implied probability

**= 1 / 2.10**

**= 0.476**

**= 47.6%**

So the implied probability of Over 2.5 goals odds of 2.10 is 47.6%.

Now let’s consider the Under 2.5 goals.

Bookmaker B, Under 2.5 goals, 2.05

Implied probability

**= 1 / 2.05**

**= 0.4878**

**= 48.78%**

So the implied probability of Under 2.5 goals odds of 2.10 is 48.78%.

To work out if we have an arb available to us, all we need to do is simply add the implied probabilities.

**Total: 47.6% + 48.78% = 96.38%**

When the total implied probability on a betting market is less than 100%, you have discovered a surebet arbitrage opportunity. The lower the total implied probability, the greater than value you have found.

Let’s consider another example. An NBA game between the Boston Celtics and the Chicago Bulls has the following best odds available:

Bookmaker A, Boston Celtics, 1.30

Bookmaker B, Chicago Bulls, 7.00

Bookmaker A, Boston Celtics, 1.30

Implied probability

**= 1 / 1.30**

**= 0.7692 = 76.92%**

Bookmaker B, Chicago at odds of 7.00

Implied probability

**= 1 / 7.00**

**= 0.1429 = 14.29%**

Market Total

**= 76.92% + 14.29% = 91.21%**

Once again, we have found an opportunity to secure a guaranteed profit with the total combined implied probabilities below 100%.

While discovering surebets is one thing, key to exploiting them is in calculating the optimal bet stake.

This is easy in some cases, for example when the odds are identical. But in practice, most odds are imbalanced and require us to weight our stakes accordingly. How is this done? There are three steps:

1 – Calculate the implied probabilities of each market outcome.

2 – Calculate the sum of all implied probabilities.

3 – Divide each outcome implied probability into the sum of all implied probabilities.

Doing this allows us to determine the optimal bet stake to secure our guaranteed profit.

Let’s reconsider our NBA example: Boston vs Chicago

First, we calculate the implied probability for each of the two outcomes and then add them together.

Bookmaker A, Boston Celtics, 1.30

Implied probability

**= 1 / 1.30**

**= 0.7692 = 76.92%**

Bookmaker B, Chicago, 7.00

implied probability

**= 1 / 7.00**

**= 0.1429 = 14.29%**

Market Total

**= 76.92% + 14.29% = 91.21%**

To determine the optimal bet stake we divide the implied probability of each outcome by the total market implied probability.

Boston

**= 76.92% / 91.21%**

**= 84.33%**

Chicago

**= 14.29% / 91.21%**

**= 15.67%**

So let’s say we want to arb a total of £100. In this example, we would place 84.33% of our £100 on Boston and 15.67% of our £100 on Chicago.

Our wagers would look something like the following.

**£100 * 84.33% = £84.33 on Boston at odds of 1.30**

**£100 * 15.67% = £15.67 on Chicago at odds of 7.00**

So regardless of what happens in the game, we are guaranteed a profit of roughly £9.66.

If Boston wins, we collect (£84.33 * 1.30 – £100) a guaranteed profit of £9.63.

If Chicago wins, we collect (£15.67 * 7.00 – £100) a guaranteed profit of £9.69.

But what about football matches you ask. Or even a horse race featuring 10 or more runners. Well, fortunately, the very same principle applies. As stated previously:

1 – Calculate the implied probabilities of each market outcome.

2 – Calculate the sum of all implied probabilities.

3 – Divide each outcome implied probability into the sum of all implied probabilities.

So then let’s say that we have an upcoming Premier League match between Liverpool and Manchester United.

Best odds available are as follows:

Liverpool win, at odds of 2.90

Drawn match, at odds of 3.50

Manchester United win, at odds of 3.10

Do we have a surebet in the 1X2 match result market? Let’s see.

As we did in our earlier examples, we need to first calculate the implied probability for each possible outcome.

Liverpool win at odds of 2.90

Implied probability

**= 1 / 2.90**

**= 0.3448 = 34.48%**

Drawn match at odds of 3.50

Implied probability

**= 1 / 3.50**

**= 0.2857 = 28.57%**

Manchester United win at odds of 3.10

Implied probability

**= 1 / 3.10**

**=0.3226 = 32.26%**

So now we total each probability to come to our market total.

**= 34.48% + 28.57% + 32.26%**

**= 95.31%**

Yes, we have found an arbitrage surebet opportunity as the market total is under 100%.

The next step is to work out how much we need to bet on each outcome so as to reward ourselves with a balanced profit regardless of which outcome is the winner. Let’s say then that we want to invest a total of £200.

Liverpool to win at odds of 2.90

**= 34.48% / 95.31%**

**= 36.18%**

So we will stake 36.18% of £200 on Liverpool to win, a stake of £72.35.

Drawn match at odds of 3.50

**= 28.57% / 95.31%**

**= 29.98%**

So we will stake 29.98% of £200 on the drawn match, a stake of £59.95.

Manchester United to win at odds of 3.10

**= 32.26% / 95.31%**

**= 33.85%**

So we will stake 33.85% of £200 on Manchester United to win, a stake of £67.70.

If we bet each of these amounts, we will have a sure profit on this match market of roughly £9.85. No matter what happens in the match, we will receive this profit.

*Harder Than It Looks*

*Harder Than It Looks*

Of course, arbing is harder than it seems. The first issue is that most arbitrage opportunities are available for only a limited time. It is rare for a surebet to be available for longer than fifteen minutes. Many professionals have even developed tools that alert them to arbitrage opportunities, giving them the chance to take advantage as soon as the opportunity presents itself.

Another is issue is that for each arb, the profits are relatively low and require high turnover to scrape out a meaningful profit over the course of a year. In fact it will be rare to find an arbitrage opportunity greater than 3%. In order to be a profitable arber, you have to invest a great degree of capital and often a great degree of time.

We also need to take into account the fact that bookmakers will limit and in some cases, close accounts that they believe are arbing. While this may be considered unfair it is how it is and an obstacle any successful aber has to negotiate. The easiest way to avoid being tagged as an arber is to bet with inexact stakes. For example, if you calculate an optimal stake to be £27.10, place a bet of £27 or better yet, a bet of either £25 or £30. It may not give you the precise profit you expect, but it will help keep you under the radar.

## Value Accumulators

If you’ve ever wondered why bookmakers promote accumulators aggressively, it’s due to the fact that most punters don’t know how to identify betting value and the additional fact that accumulators consisting of negative value selections generate huge profits for bookmakers right throughout the year and especially the football season.

Why are accumulators typically such horrendous value? Well, it is due primarily to the margins that bookmakers take out of their odds. Let’s look at a simple example, a 5 selection Asian handicap acca for an upcoming weekend of Premier League football. Our acca consists of the following selections:

**Liverpool +0.5, 1.90**

**Chelsea -1, 1.90**

**Arsenal -0.5, 1.90**

**Tottenham -0.5, 1.90**

**Everton +0, 1.90**

Here we have five selections, each priced at 1.90. To calculate the odds of our acca, we simply calculate each price into the next.

Doing so gives us odds for this of 24.76.

Now let’s calculate those odds again, but this time we use the fair odds (without any margin taken out) of 2.00.

Doing so gives us odds of 32.00.

So while the margin on each selection was just 5%, I.e 1.90, as opposed to 2.00, the margin on our 5 selection acca, becomes a whopping 22.6%.

To put it in perspective, if you were to bet on a single Asian handicap selection with a margin of 22.6%, your odds would be roughly 1.55, in comparison to the margin free fair odds of 2.00. Would you place a bet on a single Asian handicap a these outrageously poor value odds? Of course not.

*Multiplying Your Value*

*Multiplying Your Value*

But here’s the trick.

If you only include selections that are of genuine value, you actually increase the value of your acca for every value selection that you include.

Let’s say we have 3 value selections for an upcoming Premier League weekend. We have:

Liverpool to win at odds of 2.10

Chelsea/Tottenham to go Over 2.5 goals at 1.90

Newcastle/Everton to draw at odds of 3.50

We have made our calculations and believe each of these to be valued selections.

Liverpool are a 50% to win

**0.5 x 2.10 = 1.05**

Chelsea/Tottenham are a 55% chance of going over 2.5 goals

**0.55 x 1.90 = 1.045**

Newcastle/Everton are a 30% chance to draw

**0.3 x 3.50 = 1.05**

As we can see, each selection is a value selection I.e it is over the value of 1.

The odds we will receive from our bookmaker for this 3 selection acca will be 13.97.

Now you may be saying, so what? Well here’s what. Let’s calculate the probability for this acca based on our assessed probabilities:

**0.5 x 0.55 x 0.3 = 0.0825**

The probability of this acca winning based on our assessed probabilities is 8.25%.

Let’s then calculate the value of this acca.

**13.97 x 0.0825 = 1.153**

So there we have it. While each of our selections on their own was of around 5% value (1.05), combining them into a 3 selection accumulator increased that value to over 15%. Not too bad.

So while recklessly placing accumulator bets of negative value will only see you severely diminish your chances of being a long-term profitable bettor, by including selections of genuine value, you increase your chances significantly.

What’s even better is that while being a profitable bettor long term may see your betting account limited or even closed, by placing accumulator bets you signal to your bookmaker that you may be just another loser willing to accept poor value odds. In fact, many bookmakers encourage accumulator bets by offering enhanced returns on accumulators all the way up to 12 selections giving you even great chance to earn consistent profits. You may have seen acca bonuses offering 50% profit bonus on acca of 6 selections. Taking advantage of these offers is well worth your time.