The average mutual fund has lost about 2.5 percent a year to taxes on dividends and capital gains. Most funds are managed without regard to taxes, but taxes are something that can be controlled.

You have some flexibility.

Say we have to sell shares of Cisco to match its standing in a particular index. We sell the shares we have with the highest cost basis.

This is a natural evolution of what we have long talked about at Vanguard -- that costs, broadly defined, are important in assessing funds' returns.

Distributions are no reason to panic, ... What you're doing if you sell is realizing all of your gains. You're selling your fund and you're creating a taxable event.

You've accelerated your liability.

These costs do add up over time.

You have to take each situation individually, ... Don't make a knee-jerk reaction.

Taxes are the single largest cost for shareholders.