This suggests a possible scam (probably not an original suggestion). Set up some large-enough number, maybe 30 or 40, shell investment companies. Each one trades according to a very specific but randomly generated strategy, which it publicly announces in advance. (Some care would have to be taken in generating the strategies, but they should be such that they're expected to match the market, when taken as an ensemble.)

After a few years, some of these strategies will have turned out to be successful, others haven't. Quietly wind down the unsuccessful ones. The successful ones now look prescient: this firm announced in, say, 2008, that the market conditions were such that strategy X is clearly correct going forward. And history has now borne them out: here, five years later, their prediction was right and their portfolio is up 1000%. Of course, there is missing information, that this was just one of 40 shell companies, and overall returns across all companies did not beat the market. But now this successful company can sell investment services/consulting/whatever on the basis of its individual track record.

I suspect actual investment consultants are effectively doing a distributed, non-coordinated version of this, even if not intentionally.

[1] http://ask.metafilter.com/216295/Is-this-famous-investment-s...

A recent grad looking for a job with an investment bank picked 64 banks and sent each of them a letter introducing himself. To a half of them he also added that next week Ford stock will be up and to other half he said it would be down.

Next week, one half of the banks were off the list, because he was wrong. He split remaining banks in half again, sent another letter making his up/down prediction and repeated again for 4 more weeks. After 6 week there was just one bank on the list, but it was the one that saw him make an accurate prediction 6 times in a row. And so he sent them the job application.

https://en.wikipedia.org/wiki/List_of_works_by_Derren_Brown#...

My bank advised me to invest in "Investment Fund #17": their headline info was that this fund marginally beat market average in each of the last 3 years.

I decided to invest elsewhere.

But here's what I don't get. It seems like such a reliable and lucrative scam that there should be dozens of managed funds who have grown by 1000% over the last 10 years. Where are they all?