Risky business

I run multiple systems.

Over multiple markets.



A few months ago I added a new system.

To trial within my portfolio.

The numbers were good.

A nice profit year on year.

I ran it with a small bank.

Recently my data provider said some of their data had been miscalcuated.

My YoY winning system.

Turned in to a YoY losing system.

Fortunately I was still in test mode.

So only risked a small bank.

No matter what the data says.

What your backtesting suggests.

There’s always risk.

This system was sports markets.

Using betfair.

Always trial any new system.


  • Is your data correct 100%
  • Variance in past prices vs prices you can realistically get going forward
  • Data provider has tech issues
  • You miss some trades
  • IT issues
  • Betfair / trading partner issues
  • Not getting matched / fully matched
  • Human error

Always build variance in your systems.

Whatever my backtesting says.

I always reduce potential profits by 25%.

Negates the random issues you will encounter.


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