Which Index Fund Is Right For You? Two Types Look Alike S&P 500 and Total Stock Market nose each other out in various periods.(MUTUAL FUNDS)(THE BASICS)

Byline: MURRAY COLEMAN

Finding a stock fund that has outperformed the market is easy, but finding one that will outperform is a tougher -- many say, an impossible -- task.

Some funds outperform in one period, but then lag in another. The fact that the broad market itself has produced returns that beat other asset classes over the long haul make index funds a viable option for long-term investors.

But once you've made the decision to put your assets in an index fund, you run up against another choice: S&P 500 or total stock market?

The two types of index funds have much in common, but some notable differences. The key question is: Does it matter which you choose for long-term investing?

By most accounts, not much.

S&P 500 funds are based on Standard & Poor's index of 500 handpicked companies. They operate in a variety of industries and are weighted in the index by market capitalization (market price times shares outstanding).