The Mirage of Success

In Chapter 22, Larry Harris asks the million-dollar question: Are you a genius, or just lucky? Most people trade because they want to get rich quickly, but few realize that beating the market is one of the hardest things in the world.

The Components of Performance

Your portfolio return is made of three things:

1. The Market: If the whole market goes up 10%, you didn’t “do” anything. A rising tide lifts all boats.
2. Risk (Beta): If you take twice as much risk as the market, you should get more return. That’s not skill; it’s just a “risk premium.”
3. Skill (Alpha): This is the value you added by picking the right stocks or timing the market. This is the only part that actually matters.

Relative vs. Absolute Returns

An absolute return is just “I made 20%.” A relative return is “I made 20% while the market only made 10%.”

Relative returns are much more informative. If you make 15% when the market makes 30%, you actually performed terribly. You would have been better off doing absolutely nothing and just buying an index fund.

The Problem with Benchmarks

To find your Alpha, you have to compare your results to a benchmark (like the S&P 500). But if you are a small-cap trader, you can’t compare yourself to the S&P 500 (which is large-cap). You need a benchmark that matches your “style.” Otherwise, you might look like a genius just because your style happens to be in favor this year.

The Statistics of Luck: Student’s T-Test

Harris gets into the math here. To prove you are skilled, you have to show that your returns are too high to be explained by luck alone.

• The Problem: The “noise” of the market is massive. Because of this, it is statistically impossible to distinguish a “skilled” manager (who beats the market by 2% a year) from a “lucky” manager unless you have at least 20 years of data.
• The Trap: Most people pick a fund based on “last year’s performance.” Harris shows that last year’s performance has almost zero correlation with next year’s performance.

The “Genius” of 10,000 Monkeys

Imagine 10,000 people who know nothing about stocks. They all flip a coin every day for a year.

• By pure chance, one of them will flip “heads” every single day.
• That person will look like a “Grand Master of Coin Flipping.”
• The financial press will interview them, they’ll write a book, and people will give them millions to manage.

The same thing happens in the stock market. In a world with thousands of fund managers, some will have a 5-year winning streak purely by chance.

In the next part, we’ll look at the “Survivorship Bias” and why you should be very skeptical of any “successful” manager you see in an advertisement.

Next Post: Survivorship Bias and the Future of Performance (Part 2)