Lima: That’s a good point, and upon further research, I’m issuing a correction here and removing this sentence from the article: The stock market is, after all, a zero sum game: For every winner, there is a loser.

Zero-sum games are, as you knew, closed systems (like a poker game) in which there is a fixed amount of money to be won or lost by the participants. Because stocks can rise in value over time, due to economic growth or other inputs, and the rise of one stock does not portend the necessary fall of another. The whole system is not a zero-sum game.

Removing that sentence doesn’t materially change the article—an individual still can’t expect to “beat the market.” But it was included in error and I’m glad you pointed it out so I could correct it. Thanks!