Martingales are psychologically dangerous because you get continuous positive reinforcement for doing something that actually has negative EV. Martingales generate a steady stream of profits until suddenly they generate huge losses. Potential martingale trades include: 1. mean reversion 2. trend following 3. selling options 4. selling vol 5. being short single stocks 6. being long bonds 7. anything derived from backtesting (inevitable risk that the long tail of negative outcomes isn't represented in the history) 8. anything that uses leverage 9. anything that uses 'stop losses' assuming liquidity will exist 10. Merger arb Remember, a long stream of impressive returns multiplied by zero is still a zero.
The only time I have heard of this rule was in roulette ...it works but it doesn't since their is a max bet you can apply at the table or the other idea that you may not be able to fund the bet after too many continous losses
Brilliant Post, Thanks @ScroogeMcDuck -- unfortunately, most will not value your post as a result of not really understanding market structure and pricing risk ...
I think you need to understand what a martingale system is. Every single point that you have enumerated is just part of trading and might or might not have anything to do with martingales. A martingale is not a a series of wins followed by a loss. It is actually the opposite, a series of losses where the gambler increases the size of the bet on every attempt aiming to cover previous loses. Whilst it is true that martingales are dangerous just because the rely on the ability to have infinite money, what you have described have nothing to do with it.
This^^^^^ The classic is buying down to get a better cost basis until it becomes a pyramid down loss and it blows up. You escape a loss temporarily and avoid a loss (and gain) when you exit BE. The problems are: Buying down can be going against a trend and the pain will get to Max. Can't buy down anymore because lack of funds. Margin call. But the real issue is before the disaster. Your trade can be simply wrong and there is no mechanism to right the ship. Opportunity is lost with both time and funds being deployed for winners The self delusional nature of "never loosing" Crap risk control. There are so many better ways. OTH hand if you pyramid up, i.e. the opposite, that is not the answer either. That is also a simplistic strategy and eventually all trends end, sometime violently. The reason I bring up the "opposite" is to demonstrate, the notion is so incomplete* that it does not matter which way, it needs additional tactics. Hence, it is better to go for a different method entirely, such as cutting losses quickly and hedging the winners. *e.g. it does not even take into account the speed(time) it takes for a loss or gain to occur, which is basic stuff.