You're both right. There are traders who beat the market in a way that's clearly statistically significant and doesn't involve selling tail risk or other cheats

You're both right. There are traders who beat the market in a way that's clearly statistically significant and doesn't involve selling tail risk or other cheats. However, they can stop being successful at any time. To give a concrete example, GETCO circa 2009 was the premiere HFT firm trading 19% of US equities market volume and earned high 9 figures in trading profits on a tiny capital base. They were doing millions of little trades daily and made profits almost every day, if not every day. The odds of someone doing that due to chance are infinitesimally small. They had been doing this since the early 2000s, quietly building an empire, and the people there were incredibly bright. They had their pick of the litter from every top school and one of the toughest interview processes. Retention was impressive, too, as the firm made many employees into millionaires in their early 20s and gave them plenty of autonomy. You'd look at this operation and expect it'd never end. But it did, and quite quickly. Competitors eventually learned what they were doing and saturated the market. Their market share plummeted, as did profits, while the cost base grew. High speed data and microwave lines became a new cost of doing business. Layoffs happened. Once loyal employees defected and with them went even more of the firm's ideas. Eventually they got a soft landing by buying out KCG, and the entire operation was later acquired by Virtu, but from what I understand, few of the original GETCO trades still exist or make any profits. So I believe they won due to skill at the time, not luck, but more skillful competition came along to replace them. Some small group will always beat the market, but I'd need more evidence to believe one group would do it for a long time. Brain power and guarding IP are necessary but not sufficient.