It doesn't matter if losses out
number wins - as long as they don't out
weigh them. Many a good trader consistently (and happily) has more losses than wins.
If a cull is required, I don't fret about the number involved. If there are losses to be zapped I do it fast so they die small rather than grow and die big. I certainly wouldn't allow any quota to get in the way of that.
It is perfectly possible to lose more often than you win and still be regularly making a profit. Some traders who cut their losses extremely fast don't ever need to get half their trades right, and are happy with a 40% success rate.
You need to keep track of your average win size and average loss size, otherwise you won't know what success rate is necessary.
If your average win is over 50% bigger than your average loss, you can make a profit from winning 4 times out of ten, and losing six times.
Tighten the losses so they average a third of your average win size, and you can stay in profit with 3 wins out of ten. Which gives you a heck of a lot of leeway if your selection skills are not yet very good.
Someone who lets their losing trades slip to -15% before dumping them, while snatching at 5% gains, will need to win more than 7 out of every ten trades, which is a tough call.