I love that MyFXBook provides a value for monthly return, this is super useful. Unfortunately, people abuse this. You see it all the time, they start with a really small account, and trade super aggressively for a month or 2. If they blow up the account, no matter, it was only small, and they start again. If they make a couple hundred %, perfect, then they start to trade normally.
Once their account is 12 months old, they are really doing 5% profit per month (or maybe even losing), but the stats say 20% per month because of the false first couple months.
Here is an easy fix for this... give a weighted average month. So the first month ever gets a weighting of 1, the second month gets a weighting of 2, and so on... this way those first couple of false months have much less bearing on the score.
Not only that, but this is also a very useful number even aside from the scammers. A system that is doing well recently is more appealing than one that is doing poorly recently.