Before I have seen the musings of a fund manager posted, predicting the next downturn. Apparently he’s been doing this since before the last downturn. His fund is barely above flat since inception in the early 2000s, even though the S&P has more than doubled. After pointing out all that, I still got some respondents who claimed that active funds are known to underperform during good times and outperform in bear markets. Perhaps it is true but I remember feeling skeptical.

I guess there is no evidence that will convince everyone that someone is a bad money manager or prognosticator. That’s why, despite my general discomfort with Nassim Taleb, some of what he said in Skin in the Game really seems true. People can believe what they want, but beliefs don’t matter much if they aren’t confirmed, and the only meaningful way to confirm or reject market beliefs is via investment results.

Suppose you have someone that says "amazon is overvalued, there's no way they are worth more than $400B" over and over again for years as Amazon goes from $600B to $900B. I'd still keep an open mind as long as the market in general was irrationally exuberant over that period. It's only once the market as whole returned to sanity and most stocks went down, but amazon continued to raise that I'd say that guy probably doesn't know what he's talking about.