Don't put all your portfolio in a single trade -why?

2022年3月16日

I was reading about maths and came across this very nice explanation, that we can apply to especially trading and also to investing in a very obvious way. We all know and are told not to put it all down to a single trade. Too risky. Crazy. But you can bet it all and get rich!
Well, just look at these numbers below:

[adapted from https://towardsdatascience.com/understanding-random-forest-58381e0602d2#:~:text=The%20random%20forest%20is%20a,that%20of%20any%20individual%20tree].

Imagine that we are playing the following game:
I use a random number generator to produce a number. If the number I generate is greater than or equal to 40, you win (so you have a 60% chance of victory) and I pay you some money. If it is below 40, I win and you pay me the same amount.
Now I offer you the the following choices. We can either:
Game 1 — play 100 times, betting $1 each time.
Game 2 — play 10 times, betting $10 each time.
Game 3 — play one time, betting $100.
Which one would you pick?

...
...
...

Outcome Distribution of 10,000 Simulations for each Game:
(this is a super-crude and inexact approximation to the plot you can see on the website I linked above, but you see the gist).
The "---" are the 100$ 1-time bet, followed by the 10$ 10-time and the 1$ 100-time ones.
(ignore the plot frame, just look at the text box within the plot. This was the only way I could figure out to introduce formatted text in this post!)


Seeing this, now which game would you pick?
Game 3 offers the chance to win big money, and to lose it all, at a flat 60% chance of winning. In Game 1, however, you win less money, but look at the consistency... you traded 100 times and you make money in 97% of them (believe the numbers, otherwise check the above link)!

Note that this example assumes a 60% winning chance, so you are not opening a position at random but based on indicators that increase your chance of a win. You can run your own numbers for a 50% winning chance.
Happy trading!