Automated traders need to chime in here. Some of them do very well with ridiculously low win %. Necessary win % is dependent on the methodology structure.
since you asked, the win ratio depends on the duration your measuring, yes there is time we, or
Perhaps i have ultra low winning % but the loss is so small where you can afford to get hit 20 times and the one trade that makes it covers all the losses. It also depends on if your measuring over all performance or per instrument measurement, most of the time at least for me i do NOT heavily calculate this ratio because out if 10 hands dealt there is no way to know which one is winner or loser and again duration gets involved the winners/loser ratio can again be affected, being systematic i take every signal. Winner or losers i cant and i do not input my feeling and i follow it no matter what , After recent mayhems and wild swings, ive changed my systems to trade only instruments with options, because systematically you cant accurately calculate losses forward looking if the instrument gaps against you but you can if your buying options. This caused a massive shuffle in instruments being traded
so whaat the win ratio? Depends on duration and depends if your talking entire systems calculation or per instrument calculation but as others mentioned here its not as important as knowing how much you can lose in the worse of the worse situations
most importantly this to ANY trader, automated, systematic, or discretionary or whatever is
Position size because even if you got 90% winning ratio you can fuck it up if you take a larger position or smaller on that one losing trade which obviously you wont know in advance this happens because people tend to be emotionally connected to an instrument or think its too cheap (like me in crude oil) or too expensive (like me in palladium) but worse sometimes its happening and they do NOT knwo at all in my experience most traders maybe not here hardly know what ot means to systemize position size, you ask them what size you took on this and that and u get two different answers and if u ask why they be like oh this stock is 20
Bucks and this one is 80 bucks yet you will
Find the size they took on the 20
Dollar stock is 3 times higher than the position they took on the 80
Dollar stock
this can fuck it up all
edit: even the same amount of contracts all the time is not the same size, because the value of those contracts notional changes daily even though margin might not right away, like the es for example, 2 contract when its at 3000 is not the same as 2 contracts when its at 2500