As long as you assume 50/50 minus trading cost your expectancy is negative.
No amount of money management (i.e. martingale) will change that.
Therefore mathematically to last in the long run you need an infinite account.
With a fixed size account the best you can do is choose your desired probability of ruin and from that compute you return. Note that that will not change your long term expectancy as ruin is inevitable.
If I remember correctly from the top of my head (it's been a long time but you can easily do the calculation by making a few assumptions) for a probability of one ruin every 50 years your return is less than CD by a factor 10-15.
In any case it's a loosing proposition (i.e you can't make enough before ruin happens).
Now if you have a stationary return process and you know its parameters (mean/std) then that's a different story...
Ninna
No amount of money management (i.e. martingale) will change that.
Therefore mathematically to last in the long run you need an infinite account.
With a fixed size account the best you can do is choose your desired probability of ruin and from that compute you return. Note that that will not change your long term expectancy as ruin is inevitable.
If I remember correctly from the top of my head (it's been a long time but you can easily do the calculation by making a few assumptions) for a probability of one ruin every 50 years your return is less than CD by a factor 10-15.
In any case it's a loosing proposition (i.e you can't make enough before ruin happens).
Now if you have a stationary return process and you know its parameters (mean/std) then that's a different story...
Ninna