[throwawaymath]

You keep talking about this data, but you're not citing any of it. Therefore I'm not sure how to specifically counter what you've read.

But in the abstract, you differentiate them the same way you implement any hypothetical distinguisher in probability theory. Consider an n-sigma event observed to occur consistently. As n increases the likelihood of the event occurring by chance (rather than agency) decreases.

[xorfish]

https://www.aei.org/carpe-diem/more-evidence-that-its-really...

There are so few managers that beat the market and then it might still be luck. Until you can be sure that a manager really is concistently better than the market he will be in his sixties.

We know factors that concistently outperform the market. So why not passively follow them?

[throwawaymath]

There are so few managers that beat the market and then it might still be luck.

This is a naive way of doing the analysis, because we have examples of funds whose performance is so many standard deviations beyond the mean that we wouldn't expect them to arise by chance even if every single business in the United States was a professional trading firm. To get you started, I invite you to consider Renaissance Technologies, as one example. [1]

We'll assume that trading returns have a binary distribution. Traders win or lose with equal probability. This is not a great model, but it's good for making ballpark estimates, because it overestimates the odds of a track record like Renaissances.

RenTec's Medallion fund has not had a down year in the past 25. The odds of this are at most 1 in 33 million, using our binary model. Survivorship bias does not begin to explain this; there have not been anything resembling 33 million hedge funds over the course of history. I think 30000 hedge funds is a fairly generous estimate. [2]

In order to account for Renaissance's 30 year record of 70% returns before fees (and 40% after fees) under your hypothesis, we need to advance the claim that Renaissance has been successfully conducting massive fraud and financial conspiracy with a resulting profit north of over one hundred billion dollars over three decades. Even the common citation of the IRS case with the Deutsche basket options doesn't even begin to control for those kinds of returns; there would have to be something fundamentally novel criminal conspiracy occurring in Long Island.

Of course, you can still try to defend that position. But it makes the claim significantly more complex than simply saying, "most managers don't beat the market."

_______________

1. There are others. TGS, Baupost, etc.

2. This is copied from one of my favorite rebuttals of this point: https://news.ycombinator.com/item?id=9860254

[xorfish]

I get that there is a very small window for funds that have alpha. However they are of no use to the average investor. Either they are closed to new investors or they are open and the performance edge goes away after some not too long period. Which is also the reason they stay closed.

Stocks don't have a 50% chance of being up per year. It is more close to 80-90%. The size of the return however makes a really good case that Simons fund is better than the other managers at discovering prices.

https://www.slickcharts.com/sp500/returns

I don't think we can be sure that Baupost's performance is not due to luck. Since 2001 it is reported to have an annual return of 9.4%, that is decent but not much above the market.

In the end, the average investor will not be able to invest in a fund that has consistent alpha. The alpha that a fund has will get smaller the bigger the fund gets. Just look at the recent performance of Berkshire Hathaway.

[thedudeabides5]

What's a factor?

Sounds like just another manager.

[xorfish]

Factors are for example market, size or value. Over long periods of time they outperform the risk free rate or the market.

https://www.investopedia.com/terms/f/famaandfrenchthreefacto...