These have been tough times for strategic long term investors. While it may seem logical to stay the course through the market’s inevitable ups and downs—taking advantage of stocks’ tendency to deliver strong returns over very long periods—that logic was little comfort during the bear market, when some portfolios lost more than half their value. Wouldn’t it have been better to bail out in, say, late 2007, replacing stocks with cash or with bonds, which have outperformed equities during most of this decade?
Of course it would have been better, but myriad problems stand in the way of executing a successful market timing strategy, which calls for getting out of investments before they swoon and getting back in when they’re ready to rise. To investigate market timing’s feasibility, Donald Bennyhoff and Yan Zilbering at the Vanguard Group recently examined the performance of the Standard & Poor’s 500 stock index from 1928 through 2008 and reported their results in a research note, “Market-Timing: A Two-Sided Coin.” Looking only at prices—they left aside dividends because of a lack of data on daily total returns before 1980—Bennyhoff and Zilbering found that the index had returned an average of 5% a year during that 81-year stretch. A clairvoyant investor who had managed to be out of the market on just the 20 worst trading days—avoiding an average loss on those dark days of 9.2%—would have gained 7.5% annually. Anyone who had missed the 20 best days, on the other hand, would have gained only 2.6% a year. That amounts to a 50% swing, up or down, in portfolio performance.
No one could ever hope to forecast all of the market’s best and worst days. But given that infinitesimally small changes—being out of the market on just 20 of 20,340 trading days during the 81 years the researchers considered—can have a profound impact, it may seem worthwhile to try to identify some of them. What if, for example, you got out of the market after it had a particularly bad day, or got in after a really good one? Wouldn’t more of the same be likely to follow?
Often that’s not the case, according to Bennyhoff and Zilbering. Frequently the best and worst days happen within shouting distance of one another, and some of the best days have been particularly likely to follow hard on the heels of some of the worst. In dramatic turnarounds, eight of the 20 best days occurred within 10 trading days of one of the worst 20 days. On October 29, 1929, the S&P sank by 16.1%; the next day, it soared 12.5%. In 2008, a 7.6% loss on October 9 was followed by an 11.6% gain on October 13.
Post-plunge rebounds often last more than a day, with the market frequently recouping, during the next few weeks, a significant fraction of what it has lost. For example, the worst sell-off in the Vanguard study—on October 19, 1987, when the S&P 500 lost 20.5% of its value—was quickly followed by a lot of buying. Within 20 trading days of Black Monday, the market had rebounded by 9.6%. A similar thing happened during the 1929 crash; after that 16.1% free fall on October 29, the S&P stabilized temporarily, regaining 2.5% during the 20 trading days that followed. And in 2008? Twenty days after December 1, when the market fell 8.9%, it had regained 9.1%. Looking at the S&P’s performance following all 20 of the worst days, the market regained an average of 2% during the next 20 trading days.
For would-be market timers, those tendencies make a difficult job virtually impossible. While it may be feasible to anticipate broad market shifts and to make tactical adjustments to a portfolio based on certain metrics like price-to-earnings ratios, any attempt to time a wholesale market entrance or exit will probably fail. Few people expected the stock market to surge when it did in the spring of 2009, or to advance as much as it did during the next several months. Investors who had cashed out their portfolios during the market rout almost certainly missed some (if not all) of the rally.
The recent volatility of the S&P 500—from day to day, week to week, and month to month—only reinforces how unlikely it would be for anyone to get in or out at just the right time. Rather than try to time the market, which almost always backfires, most investors would do better to stick with a well-diversified portfolio with regular asset allocation rebalancing to keep volatility in check and increase potential long-term gains.
Performance data quoted represents past performance and does not guarantee future results. Indices are unmanaged and do not reflect the payment of fees and other expenses associated with an investment. Investors cannot directly invest in an index.