The Wall Street Journal’s Jason Zweig says many money managers are failing to use a fairly simple tactic — portfolio rebalancing — that could be costing clients a good deal of money.

“Investment professionals are supposed to exercise independent judgment; in Warren Buffett’s words, they should be fearful when others are greedy and be greedy only when others are fearful,” Zweig writes. “It doesn’t always work that way. Corporate pension funds had 69% of their assets in stocks in 2007 as the market hovered at record highs. They have slashed that exposure to 45%. … Advisers, too, have been buying higher and selling lower. Those who use TD Ameritrade had an average of 26% of clients’ assets in bonds and cash on Oct. 9, 2007, the day the Dow Jones Industrial Average hit its all-time high of 14164.53. By March 9, 2009, the day the Dow scraped rock bottom at 6440.08, the advisers had jacked up bonds and cash to 51%.”

Zweig says it appears to be not only a failure to rebalance, but also a push to move further in the opposite direction a rebalancing would take you. If you started with a similar allocation to the TD Ameritrade 26% bond/cash exposure at the peak of the market in 2007 and did nothing, the market’s plunge would’ve brought the bond/cash portion of the portfolio to 47% in March 2009 — still short of the actual 51% figure. And as of the end of September, the cash/bond allocation would’ve fallen to 34% if left untouched — far below the level many funds currently have.

And Zweig says a recent Charles Schwab survey indicates that, even though bond prices are near record highs, most advisors plan on upping their bond allocation. All of this indicates that “financial advisers have been unbalancing instead of rebalancing their clients’ accounts,” Zweig says. “By selling stocks as they fell and buying bonds as they rose, advisers may have ended up exposing clients to more risk, rather than less.”

Zweig also offers some explanations for why managers and advisors may be failing to rebalance.