Focus on the future, not the past


Here are the year-to-date returns, through the end of June, for the five basic Thrift Savings Plan funds:

  • C Fund = 9.34%
  • I Fund = 14.10%
  • S Fund = 7.41%
  • F Fund = 2.48%
  • G Fund = 1.17%.

Interesting? Maybe to some. Useful? I don’t know how.

As an investment manager — or TSP participant, as you are commonly known — you are responsible for making or delegating the making of a massive series of decisions. Some of these decisions, like whether you contribute to the Roth or the Traditional TSP accounts, will most likely wind up being relatively insignificant. Others, like the distribution of your money among the available funds, will be instrumental to determining your financial future. As I’ve written before, making sure that the important decisions are the best they can possibly be is your primary objective as an investor. If you’re not sure which are the critical decisions, you’d be safe to make sure that every decision you make is the best it can be.

This brings me back to the question about the usefulness of historical performance data for the TSP, or any other investment securities. Is it of any real value? I don’t believe it is. There is no strong evidence that this information, at least in the short run, is useful for predicting future results. You can’t go back and make decisions based on it. So, what good is it? Really, it’s no good at all. In my experience, it causes problems and leads to bad decision-making.

Two wrong-headed mistakes are often made. The first is the incorrect belief in the “due theory.” This is the fallacy that the probability of an independent event occurring goes up as the even does not occur: “I’ve just flipped 10 heads in a row, so the odds of flipping a tail on the next try are greater than 50 percent.” Not true!

The second, and I think more common, mistaken belief for investors is the momentum of inertia theory. This is belief that an independent series of events is likely to continue on its current path: “I just flipped 10 heads in a row, so the odds of flipping a head on the next try is greater than 50 percent.” Wrong again.

Sure, you can find historical records that support either of these theories, but that doesn’t mean they make any sense. You can find support for just about anything through back-testing large, randomly generated data sets, and a series of unpredictable events often shows surprising runs of luck, good or bad. Patterns appear to show up just about anywhere you look for them, even in random data.

Finding a pattern in history and predicting one in the future are two very different things.

As an investment manager, your job is to be concerned with two things: where you are today and how best to get where you want to be in the future. While the past has put you where you are today, you don’t need to know anything about the past to assess your current position. And the kind of historical data published for specific investment securities, like funds, is not needed for use in making decisions about how to proceed in the future. In short, this information is useless to you in managing your TSP account or any other investment account.

Even the effect historical data tends to have on investors is unreliable, if not outright dangerous. Many of the investors I’ve talked with over the years tell me they feel great when their account values have risen quickly or steadily to a new high. Likewise, they feel bad when their account values have fallen. These effects tend to make them want to invest more, or more aggressively, on the heels of good market results and withdraw their money from risky assets after bad results. Data on investor behavior confirms this. Unfortunately, it is irrational and harmful. It is rational to become more cautious as prices and values rise, and more confident in your investing as they fall. They key to successful investing lies not in tracking the price history of investment securities, but in understanding and accommodating the probabilities of their future prices. Done right, it is a prospective, rather than a retrospective, exercise. So, it’s OK to be entertained by what happened yesterday. Just don’t make the mistake of confusing this with what will most likely happen tomorrow.


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Mike Miles is a Certified Financial Planner licensee and principal adviser for Variplan LLC, an independent fiduciary in Vienna, Virginia. Email your financial questions to and view his blog at

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