@nithin 1-2% OMG. Shocking!!. I dont know if this is due to impact cost as you mentioned.
But this is not the first time I have come across this 25-30% figure. Please see the citi bank research done sometime back which available on European Central Bank website.
Again this reports speaks about 30% trader being profitable. Also note higher profitability for IB and Citi where the minimum deposit is higher. This also shows the brokerages with more experienced/serious traders do well.
One thing is for sure, I always felt I am better with Currencies than with stocks or Nifty, Bank Nifty.
I am not sure if many other traders felt this way.