I disagree. The entire anti-vaccine movement is a good example in the medical profession. People refuse to hire lawyers.

For any profession, i'm pretty sure i can find you a crackpot who is convinced they know more than the pros.

Yeah but Wall Street is also the place where success MAKES you a professional. You won't see a guy who happens to save someone's life on the street show up in the ER the next day reporting for duty as a surgeon, yet that is how Wall Street works.

"You will not see that in medical profession." - I work in public health, and this is manifestly not true.

Hell, there's even jokes about it, mostly involving Web MD and/or Holiday Inn Express.

The two aren't comparable because one is very probabilistic in nature, the other one isn't. Also medicine doesn't change as much as the market.

The fundamental difference is that trading is partially an art. Medicine is too, but like two hedge fund managers will have pretty different outcomes, but two surgeons will have similar outcomes.

Have you not heard of the antivax conspiracy people? People often think they know better that others.

That said I knew of a person working as a trader who was one a team of 20 young guys taken on fresh from uni - at the end of the year the company sacked the 18 guys who lost money and told all their clients about the 2 whizz kids who had just had an amazing year. If the professionals all knew so much I'm not sure why those 18 people would have failed to turn a profit.

That's awesome: I wonder how far you'd get by starting a trading team of 1000 (shell companies!?), trading for 5 years and then marketing "our trading group of 5 have made an inflation-busting, above market average profit for the last 5 years!". Would people throw money at you?

You have described mutual funds. See the Mutual Funds section of [0].

[0] http://philip.greenspun.com/materialism/money

If you're talking about knowing the direction of prices, which is what everyone really cares about, then both laymen and Wall Street start out on almost equally bad footing - they can each have only small predictive edge at best at best in a highly probabilistic game. So a smart and disciplined investor can do as well as or better than wall street mostly by avoiding dumb mistakes.