As I've said I consider trading to be an abstraction from the normal economic processes of society, it is purely speculative so the rewards reaped will necessarily be hard won, traders are basically placing loads of bets on stuff; no efficient society would reward them, as a class, massively. This is not to say there aren't very wealthy traders, obviously there are, but there are not that many of them, there simply can't be if society is to function. To be an effective trader you need an edge that only you are privvy to. Or you need massive balls and a big bankroll so you can double down or put money on 10 to 1 bets.
I don't understand people who just jump into trading with a certain sum of money and a target like, "I want to make 3% a week and quit my job in 3 years :cheesy:"; no offence but I really can't get my head round such a childish mentality. Why not focus on finding a niche in the market, something you can trade profitably day after day, do it with small sums (or on a sim, although sims don't provide a real picture of certain technical features of the marketplace, slippage, execution lags etc). When you have a strategy that gives you 3% a week (or whatever your target is) then pour your money into it and watch your wealth grow, but don't expect anyone to hand you the strategy on a platter.
As to what percentage of market participants are seriously profitable (by which I meant they derive a steady income which exceeds £50,000 a year from it) over the long term, I don't know but I'm guessing it is less than 10%. You probably can eek a living out of the market without having a terribly original trading strategy, but for the money you'll make you may as well spend your days saying, "Any fries with that". And aside from the perks of being able to work from home in your pajamas and tell everyone you meet you're a trader I don't see the point.
I can't see myself wanting to become a full time trader for less than £3,000 a week (and making a steady £3,000 a week trading from home will require me to see something no other market participants have clocked, which I don't see happening without very dedicated work on my part for a fairly long period of time). If I can't make that I had may as well be a lawyer, which is what my degree will equip me for anyway, or a property developer or a scrap metal merchant for that matter; there's a much greater chance of making serious money in any of those areas, obviously the potential reward from trading exceeds the potential rewards you can get by being a barrister or a scrap dealer but there are, proportionately, more wealthy barristers and scrapmen than there are wealthy amateur traders.
P.S. £3,000 a week may sound like a lot but with the effort you would have to put into developing a profitable strategy you would be getting stiffed if you were making less than that once you actually got around to putting your plan into action.