The ABCs of Behavioral Biases (F-H)
Written by Jason Hiley
Written by Andrew Hunt
One of the reasons we turn to evidence-based investing is to guide us past the misguided strategies that can otherwise cause an investor’s expected returns to run aground. That said, there is a lot of “evidence” out there. How do we determine which of it comes from sound science and which may steer you wrong?
Survivorship bias is one trick of the trade we must watch for when accepting or rejecting a performance analysis.
What Is Survivorship Bias?
Only the strong survive. This is a familiar adage because it’s often true – especially in our financial markets. That’s why it is important to remember the expression whenever we want to accurately assess a sample of past returns. Examples of a “sample” might be the returns from all actively managed U.S. stock funds during the past decade, or the returns from all global bond funds from 2000–2014.
Survivorship bias occurs when an analysis omits returns from in-sample funds that were closed, merged into other funds, or otherwise died along the way.
How Often Do Funds Go Under?
Some new funds are truly innovative, do well by their investors, and become familiar names. Less-sturdy ones may instead focus on trying to seize and profit from popular trends. For these, the expression “cannon fodder” comes to mind. They may (or may not) soar briefly, only to fizzle fast when popular appeal shifts.
In the competitive capital markets in which we operate, fund managers launch new products and discontinue existing ones all the time. Individual funds probably disappear far more frequently than you might think.
Why Does Survivorship Bias Matter?
Why should you care about the returns of funds that no longer exist?
The funds that disappear from view are usually the ones that have underperformed their peers. The aforementioned Vanguard analysis found that, whether a fund was liquidated or merged out of existence, underperformance was the common denominator prior to closure.
If these disregarded data points were athletes on a professional sports team, they’d be the ones bringing down their team’s averages. When assessing a team’s overall performance, it’s important to consider both the wins and the losses, right? Same thing with fund performance.
Instead, an analysis marred by survivorship bias is highly likely to report overly optimistic outcomes for the group being considered. While a degree of optimism can be admirable in many walks of life, basing your investment decisions on artificially inflated numbers is more likely to set you up for future disappointment than to position you for realistic, long-term success.
Moreover, survivorship bias is only one of a number of faults that can weaken seemingly solid reports. One way in which we strive to add value to investors’ evidence-based investment experience is to help them separate robust data analysis from misleading data trickery. We hope you’ll be in touch if we can assist you with your own strategies and selections in a market that is too often rigged against the individual investor.