Out of curiosity, what do you consider really exceptional returns?
Wouldn't increased market impact from publicizing your strategy magnify the effectiveness of your strategy, and not dilute it?
Great questions. [and I've edited a bit to complete what I initially wrote]
Exceptional Returns
Let's presume you could put your money in a stock index fund and earn 8-10%. Exceptional returns would be well in excess of that, but there are two nuances: leverage and volatility.
So if you could earn 2X the index fund return, but your portfolio would be down 60% in 3 out of 10 yrs, would you do that? (kind of extreme, but for the point). Are you going to use the money anytime soon?
One way to generate exceptional returns is to invest in lower returning assets/strategies that can be leveraged. If you can borrow for less than the return you can magnify the return as much as your creditors will allow you to borrow. Of course, leverage increases total return volatility.
This is why investors use the Sharpe Ratio (
https://www.investopedia.com/terms/s/sharperatio.asp) and/or information ratio (
https://www.investopedia.com/terms/i/informationratio.asp) If either of these are high, you may generate exceptional returns. But one of the causes of the financial crisis was that banks could borrow huge amounts of money (20* their equity, roughly) and then invest in strategies/assets they though were low-vol but decent Sharpe. Then some of those strategies behaved unexpectedly...
Generally the Sharpe ratio indicates the attractiveness of an asset class (Sharpe is return per unit of risk), and an information ratio tells you the amount of performance the manager adds on top of the benchmark, so think of them as quality of returns of a benchmark and quality of returns of a strategy/manager. These lines get blurred when you have very specialized assets/strategies that can't be replicated passively (such as private equity, etc.). But any *manager's* Sharpe would include the asset class returns plus/minus their skill contribution.
But however you get it, a high Sharpe can be levered to increase returns. And the lower the volatility, likely the more leverage you'll be able to apply. So if I could trade one year Treasuries and earn an extra 0.4% per year, it wouldn't be terribly interesting without leverage. But with leverage at the cost of the one year+ say 0.05...You could multiply that 0.35% "positive float" to make it a lot more interesting. Until you were trading so much that the strategy's effectiveness was diminished. All strategies have this "
capacity" limitation...
Market Impact
I imagine you are thinking that someone could tout a stock here and cause it to go up (sometimes known as pump-and-dump, depending on your post recommendation behavior). That isn't an investing strategy, it's a trade. At best it is having fun with fellow investors, at worst it is market manipulation. But the very fact of people crowding in and driving up prices is what creates capacity limitations in investing. Once the price is up, the potential returns go down. Definitionally.
Strategies are *systems*, however, designed to take advantage of inefficiency (in theory, a high Sharpe and/or information Ratio means investors are leaving return on the table by not driving the price of the asset or trade up) So if you have a *method* of trading, sort of like the fellow above, and it is high Sharpe, then telling people about it invites others in alongside you and arbitrages away your excess return. All good strategies have capacity limitations. Even asset classes do. At some point, the price of equities is too high...and then they adjust.
The most successful investors of the modern era are at Jim Simons' firm
Renaissance. Their methods are a
deep secret. 66%/year compounding consistently is extraordinary (it translates to 4.3% per month) and is considered the best track record known to man. And yet you see people claiming on the internet that they can make 5-10% per month**. Be *extremely* skeptical. There are such strategies around, but they usually arbitrage small effects (like promotional offers), and have capacity under $1000. Renaissance was doing it with billions. And they gave back ALL their client money in their main fund because they were already hitting capacity limits that would reduce returns. The inevitable destination for a killer strategy, if it exists, is all house money and top secret.
*since I'm a PM, the equivalent is dealers touting a strategy with a Sharpe over 5. Laughable.