We’ve discussed “Sequence of Returns Risk” numerous times in the past, but most of those discussions focused on how this phenomenon affects your assets in a draw down period (i.e. a time when you are spending the money you saved to cover expenses and/or generate income).
Today we want to talk about sequence of returns in a slightly different light and note a problem it poses for all savers while they are attempting to accumulate more value in their portfolios.
Average Returns…We Hate Them
There is little doubt that we despise discussions about investment returns when one references the average rate of return as justification for an anticipated accumulation scenario.
In other words, anyone who tells you that you will have X amount of dollars in your portfolio Y number of years into the future because the stock market has on average performed Z percent per year is often making a huge error in their underlying assumptions about how a particular investment (usually the stock market) performs. This error is especially profound given its inability to adequately model real investment behavior with real asset movements.
Distilling this point to its most easily understood point is to suggest that one always ask when confronted with a claim about achieving a certain investment result based on a certain quoted “average” return is whether or not the individual making the claim is referencing the arithmetic or geometric mean when making claims about average returns.
Average Return vs. Geometric Return…Why it Matters
The best way to illustrate why you need to be aware of what “average” is being used to justify investment expectations is with an example:
Assume for a moment that you plan to make a $10,000 annual investment in a passive index fund tracking the S&P500. You plan to do this for the next 10 years and then retire. Consider the two following scenarios unfolding:
Scenario 1
Scenario 2
To the untrained eye, these could just be numbers on a page showing two “different” possibilities for how the stock market could behave over this 10 year period. But look a little closer and you’ll notice that all of the annual returns are identical in both scenarios.
The difference is we simply flip them around. This means the arithmetic mean (average annual rate of return) is the same in both cases–8%. But the balance of the investment account at the end of year 10 varies greatly, by about $53,000 or 41%.
Now look at this scenario where we’ve simply mixed the returns, but have kept all of them throughout the 10 years:
Scenario 3
Again, our average return is identical to scenarios 1 and 2, but our ending account balance is again different. We usually explain this result as the difference between arithmetic means and geometric means, and that is a correct explanation. But that explanation is also somewhat esoteric and practically useless to the average American just looking to save some money for retirement.
I’d like to instead note that this phenomenon is a function of sequence of returns risk applied to your accumulation years.
Think of it like this, the only difference between scenarios 1 and 2 is when the re...