Backtesting is useless

Alright, I am done here, "traders" who want to trade unproven, non-backtested trading systems are free to do so, it's their money after all.

What are you talking about? lol. My trades are mostly backtested. I only disagreed with your hypothetical backtest result of 5 trades for the past 5 years. Too little trades. You can flip a coin 5 times and it lands on heads by chance. That's why I mentioned I will consider it if there are enough trades. Substantial enough not to be fooled by randomness.
 
Losing system X trades once a year. Here are the results for the last 5 years (in US dollars):

2020 (so far): -75,000
2019: -45,000
2018: -125,000
2017: -85,000
2016: -15,000

Total loss: $345,000

Question: how much money would you have now if you had simply bet against System X?

Hindsight bias all over the place. Even that trading system could be a huge winner in the next 10 years.
 
Hindsight bias all over the place. Even that trading system could be a huge winner in the next 10 years.

Everything you think you know, you know because of the past.

Unless you are an extremely intuitive person or a clairvoyant, of course.
 
Everything you think you know, you know because of the past.

Unless you are an extremely intuitive person or a clairvoyant, of course.

And humans usually think they know more than they really do just because they can explain a past event.
 
In the book Fooled by Randomness, Nassim talks that the history that unfolds is just one of the multiple possible ones, this makes backtesting completely useless, don't you think?
Depends on if you are a farmer or a hunter.

For farmers, backtesting is critical to check out your thesis of what to farm, when to farm and what fertilizers, etc.

For hunters, it only tells you where your targets generally congregate, where is a better place to hunt for black swans but don't expect you will bag one anytime soon.
 
And humans usually think they know more than they really do just because they can explain a past event.

And sometimes they go broke for believing that. But the remaining ones will still have based their decisions on the past.

Overrating the past is easy, but along with our sensations is everything we've got. So it's a matter of taste. Which past information do you prefer?
 
We should recognize that everyone is not doing the same thing, even though it's all called, "backtesting."

Just because one person is unable to benefit from "backtesting," doesn't conclude for the universe that, "Backtesting Is Useless."

Now, if the original hypothesis by the OP were instead, "Backtesting is useless for me;" then it would be hard to argue against such an assertion.
 
Backtesting is useless for me

Even this idea does not make any sense at all.

Trading without backtesting the system first is like jumping from a plane and THEN checking if you have a parachute.
 
Even this idea does not make any sense at all

It may not make sense to me and you if someone claims, "Backtesting is useless for me."

But my point is that you can't successfully argue against that assertion. We can't determine what is useless, or not, for others; regardless how useful it may be to us.

If you give someone a super duper tool--whatever it is, and explain to them how it works, and they claim, "it is useless for me." Then we have to conclude that that is a true assertion.
 
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