After nine years, some investors are getting increasingly worried about the continued viability of the long-running bull market. Add in the rumors of rising interest rates, and some investors are ready to make dramatic changes to their equity investments, such as moving a significant portion of their portfolio to cash or cash equivalents (money market funds or ultra-short bonds).

Changing Your Asset Allocation

Before you let your nerves rule your investment strategy, consider that changing your asset allocation based on nerves is something your financial advisor would probably caution against if you are properly allocated. There are a couple of reasons for this. First, in the investment world, keeping cash in your portfolio is referred to as “cash drag.” This means your portfolio will likely trail market returns because cash does not generate significant returns in comparison to the market over time.

The second reason is when you change your asset allocation based on nerves, you are engaging in “market timing,” which is seldom profitable long term.

Here’s the problem: While the bull market has been running strong for nine years, it’s impossible to correctly determine when that cycle will change. If you decide to move a significant amount of your portfolio to some form of cash, you could miss several more months (even years) of solid equity-market returns. Or, the market could immediately drop right after you sell—then what will you do? Will it be time to move back into equities? All your decisions will depend on correctly reading the future, not just once, but twice.

The Challenges of Timing the Market

That’s the trouble with market timing. To win, you must correctly predict market cycles. First, you must predict when to sell an asset class. Now? Next week? The end of the year? You don’t have a crystal ball, so you can’t possibly know the correct answer.

If you correctly guess when to sell, you’re not free from the market-timing trap. In fact, you’re just halfway there. Now, you must figure out when to get back in. If the market drops 600 points in a day, will you dive back in? Will you wait for a full week of falling returns or a terrible month of returns? What if you wait for a bad month, buy back in and the market continues to fall? Will you bail again?