Quote from gkishot:
If you can make money by repeatedly playing the game it can't be a 0 sum game by definition.
You can't beat roulette by betting interchangebly on black or read because it's a 0 sum game. So how come you can guess in S&P the direction but you can't guess it in a 0 sum game like roulette by definition?
Because a roulette wheel is more efficient than the markets. Every spin gives you a 50 percent chance of winning (assuming no green). Every trade does not have to have a 50% chance of winning. It is possible to increase your chance of having a winning trade and only trade high probability trades. Of course, I think most of the extremely successful traders don't concentrate so much on increasing their odds of having a winning trade as much as making sure their winners are bigger than their losers. That's the other difference between your roulette wheel and the options market. You're assumin that each trade will either make the same amount of money for you or lose the same amount of money for you. If you let your winners run and cut your losers short, you only have to have a winning trade 20 or 30 percent of the time.
It doesn't matter if one person makes or loses money in determining whether the game is zero-sum. It is the sum of all players that must equal zero.