The number could be bit lower than 98%, but I do not have any doubt that a lot ( probably at least 90%) lose money in the Forex market.
Most common reason for that is traders jump into live trading too early than they should. They do not learn how to analyze chart, money management, uncertainty of this market, etc.
They eventually learn these things after losing a lot of money and time. Then, the old saying comes into play
" Once you did not have experience in trading but had the money; now you have the experience but do not have the money to trade."