This is a fundamental principle of probability theory.
It is known as the law of large numbers.
But keep this in mind:
Randomness determines short-term results.
Volume determines how quickly results move toward expectation.
The advantage / expected value controls long-term results.
This is why bookmakers do not optimize for perfect precision.
They optimize for volume.
Their objective is to sell as many odds as possible with a built-in margin.
But this approach creates a side effect.
Pricing errors occur.
Some odds will be overpriced.
Others will be underpriced.
If you can see the difference between correct and incorrect pricing, it becomes possible to avoid bad trades entirely.
And if you only places good trades — by betting exclusively on underpriced odds — the expected value shifts.
The advantage moves from the bookmaker to the bettor.
This makes it possible to apply the bookmaker’s own strategy against them,
within their own markets.
This approach is known as value betting.
It is the only mathematically sustainable way to achieve long-term profit against bookmakers.
How people are using value betting
There is a mathematical law
behind long-term profit
in sports betting.
Bookmakers do not want people to understand how their business model works.
Because when people understand how bookmakers actually make money, they change their behavior.
Below, you will learn how the bookmaker business model works — and why long-term profit in sports betting follows a mathematical law.
How betting markets are priced
Bookmakers use data to estimate probabilities for each possible outcome.
For example, in a football match between FC Barcelona and Real Madrid,
the estimated probabilities might look like this:
FC Barcelona win 40% | Draw 20% | Real Madrid win 40%
These probabilities are then converted into odds:
40% = 2.50 odds | 20% = 5.00 odds | 40% = 2.50 odds
Finally, bookmakers reduce all odds to introduce their margin:
45.5% = 2.20 odds | 25% = 4.00 odds | 45.5% = 2.20 odds
Did you notice how the total probability increased from 100% to 116%?
That extra 16% is the bookmaker’s profit margin.
Anyone who bets at these odds has an average expected value of −16%.
The bookmaker, on average, has an expected value of +16%.
Mathematics tells us the following:
The more independent random events that are repeated, the closer the outcome moves toward its expected value.
To identify mispriced odds, a working strategy is required.
To determine whether a strategy actually works, data is required.
Often hundreds or thousands of bets.
Fortunately, systems already exist that are designed to consistently identify these pricing errors.
This is why many choose to follow signals from systems that have been tested across large data sets.