I recently read a newsletter article titled “Dangers of Market Timing”. My first thought when I saw the title was hoping that the article would contain something new. Not only was this not the case, but the sloppy data was so bad I felt like I had to say something today before I could get some real work done.
The article states that market timing amounts to gambling because it is impossible to forecast market movements, and “you run the risk of missing periods of exceptional returns.” As an example (here comes the nonsense), a $1 investment in the S&P 500 over the last 20 years would have grown to $4.84, but if you had missed the best 10 months of stock returns, the ending value would have been only $2.04.
It’s pretty easy to grab these numbers from Yahoo and throw them into a spreadsheet. I used the Vanguard S&P500 Index fund assuming reinvested dividends. The author used the April, 1990 to April, 2010 timeframe, so I used the 20 years ending June 1 to capture the latest downturn, which ”proves” the case against market timing just as well. In the 20 years ending June 1, 2010, a $1 investment would have grown to $4.43, and missing the 10 best months would have resulted in only $1.91.
Now for some results that were not mentioned. What if you missed the 10 worst months, which is just as ridiculous as somehow missing the best months, but equally likely? In this case, your $1 turned into $13.48. Doesn’t that seem worth mentioning? How about something less ridiculous, like missing the 10 best and 10 worst months? Now, the $1 is $5.43, a 22% improvement!
Now let’s get a little smarter about the whole thing. If a big positive month happens in the middle of a string of positive months (bull market), why would you get out of the market? So let’s assume we miss positive months only when they happen after at least an 8% drop, when a portfolio would likely have been moved to cash. Similarly, if a negative month comes after a positive trend it is likely you would be fully invested, so we’ll assume you experience the full month’s loss. As a specific example, the monthly returns for June-Sept, 1998 were 4.08%, -1.06%, -14.47%, and 6.41%. We’ll count the big negative return in August because the previous month would not have triggered any selling, and we’ll miss the positive return in September because August would have caused us to move to cash. This is still incredibly unsophisticated, but it’s a heck of a lot better than the brain dead 10 best or 10 worst months. The result with just a little intelligence added results in $6.36, a 43% improvement over buy-and-hold.
The conclusion is that anyone who uses a “missing the best [days, weeks, months]” argument to prove a buy-and-hold point is either being incredibly sloppy with the data, or being disingenuous. I’m open to other arguments on the topic, but not that one.

There are plenty of well-known nuggets of wisdom when it comes to investing:
One problem is that many of these nuggets and rules-of-thumb have become popular in the last 30 years. That makes sense. Most people have a tendency to base opinions on recent experience (even though 2 or 3 decades isn’t all that recent), and the experience of many investors does not go back more than 30 years. The investment world is very different today than it was in the 1970’s or earlier. In fact, mutual fund investing, which opened up access to the markets to the everyday investor, didn’t really take off until the late ‘70s and ‘80s, so it’s safe to say that most of the investing experience of the average investor has been acquired in the last 30 years. So let’s take a look at the investment environment over the last 30 years with respect to interest rates.
The chart below shows the historical return for the S&P 500, the yield of 1-year U.S. Treasuries, and the historical return of Vanguard’s Total Bond Market Index fund (normalized to the S&P 500). Unfortunately, I couldn’t find bond index data earlier than 1990.
As you can see from the chart, Treasury rates have been in a secular bear market since 1981, which corresponds to the beginning of an explosion in the stock market. Since bond prices are inversely correlated to interest rates, bonds have clearly done very well. However, the environment is about to change.
My guess is that the 30-year fall in interest rates is about to come to an end. I know this is a bold claim with interest rates hovering just above zero, but if I’m correct it means that we are about to experience a change in the investment environment. An environment characterized by falling interest rates tends to be good for bond investors who lock in yields at higher rates. It also tends to be good for stocks as the cost of money becomes cheaper and frees more dollars for investing. Obviously there are many other factors that move the stock and bond markets, but falling interest rates has been a consistent long-term influencer since 1981.
I’m not going to suggest how to modify investment strategy in light of this new environment in this article (it would make the article too long), but I do want to make the point that investments and allocations over the next 20-30 years will likely not perform like they did over the last 20-30 years. Although the scenario of interest rates continuing to drift down is pretty much impossible, there are still two possibilities that could have very different implications. Interest rates could move up to a sustainable but still relatively low level and stay there, or they could enter a new secular (i.e. long-term) uptrend. Which of these two scenarios ends up being reality will largely depend on inflation. If large deficit spending causes a devaluation of the U.S. dollar, inflation will heat up and the government will need to raise interest rates (among other things) to try to keep inflation under control. If the Fed is able to slow down stimulus, nudge up interest rates, and keep the economy growing at a reasonable rate, we may be able to avoid a big spike in inflation and the resulting rise in interest rates. The second scenario is preferable, but it is still very different than the long-term environment we have seen over the last 30 years.
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