This New York Times article quoted a revealing study that ordinary mutual fund investors are paying dearly for timing the market.

According to his data, the 200 equity funds with the largest money flows produced portfolio returns averaging 8.85 percent a year for the 10 years through 2005. But when adjusted for dollars actually at work, as Mr. Bogle has long advocated, the return of the typical investor in those funds was just 2.40 percent, annualized. That means an underperformance of 6.45 percentage points.

The data included three funds whose typical investors lagged by more than 20 percentage points — because they were late to the party or moved in and out of the funds. These were Janus Enterprise, Old Mutual Select Growth Z and Pin Oak Aggressive Stock. For nine others, typical investors posted returns that were 15 to 20 points less than they would have achieved had they fully captured the portfolios’ gains over the period. In only 2 of the 200 cases did typical investors do better — and only slightly better — than the fund portfolios themselves: in Putnam New Opportunities B and American Century Ultra.

Recognizing that investors are concerned most about their own profit or loss, not that of a fund scorecard, Morningstar, the mutual fund rating company, is about to begin publishing data that takes a step in this direction. In a preliminary run, Morningstar adjusted returns for money flows and derived what it called a success ratio: the growth of $1 of cumulative investor return versus the growth of $1 of cumulative total return.

A reading of 100 would mean exact equivalency. Anything more than 100 reflects a “positive experience� by the average investor in the fund over a given period. A reading of less than 100 means that the experience was at least mildly negative.