Not difficult, impossible. It cannot be established scientifically. No control group, no meaningful controls.

> Following your example I can imagine that there is a mechanism (I wouldn't call it surefire) that can improve your odds.

And people who write worthless "secrets of the winners" books rely on this very assumption (and on the stupidity of the average investor). If such a thing existed, one of two things would happen:

1. It wouldn't remain secret for long, therefore everyone would practice it, therefore it would become the new average market performance. End result: no secret.

2. It would remain secret in perpetuity, the owner(s) of the secret would use it to either drain the market of its capital or foment public doubt about market fairness, as a result of which businesses would stop using the equities market to raise capital. End result: no market.

So the "secret" would either destroy the market, or the market would adjust to its existence in a way that everyone would have the same opportunity. Therefore there is no secret.

> I don't think anyone is arguing that there is a deterministic legal system to beat the market. Only that some people may be skilled enough to beat the market.

I hope you now see that this is impossible.

If this 'secret' could only be applied in small amounts, then the owner couldn't drain the market. Why do you think Buffett believes large funds can't outperform?

You assume any such 'secret' is infinitely scaleable. That's an incorrect assumption.

Insider trading is an advantage that exists but doesn't fall into your #1. Has it 'drained the market' or stopped businesses from using the stock market?

First, I never said or assumed that. Second, Human greed is, in fact, infinitely scaleable. But this is a silly debate -- obviously the most likely explanation for a spectacular market performance is chance.

> Insider trading is an advantage that exists but doesn't fall into your #1. Has it 'drained the market' or stopped businesses from using the stock market?

In a word, yes -- in a number of cases, companies try to buy themselves out of the stock market, for that and other reasons (like the tyranny of quarterly earnings reports and shortsighted boards of directors).

We're off on a tangent now. We've left the original topic. And the original topic was resolved by noting the WSJ Dartboard Contest, where managers had every incentive to show what they could accomplish, but instead they failed, spectacularly, in public, for years.