One year after the collapse of Lehman Bros., the average stock mutual fund is virtually unchanged.

The question now: How to rebuild your retirement plan and recover from the bear market that began nearly two years ago. The average stock fund has fallen 28% since the stock market's peak on Oct. 9, 2007.

What should you do now? Start with a list of things you shouldn't do:

*Don't swing for the fences. To get even after a 28% loss, you have to gain 37%. But that doesn't mean you should load up on risky funds to make up for lost time. You'll just increase the odds that you'll lose more money.

Two important statistical measures will help you get a handle on risk. The first, beta, tells you the fund's relationship to an index, such as the Standard & Poor's 500-stock index. A fund with a beta of 1 rises and falls in lockstep with the index. A fund with a beta of 1.1 will rise 10% more and fall 10% more than the index. Conversely, a fund with a beta of 0.9 will rise 10% less and fall 10% less than the index.

Another useful measure is standard deviation, which tells how much you can expect a fund to vary from its average. The higher the standard deviation, the more volatile the fund. The standard deviation of the S&P 500 the past three years is 19.6. AIM China fund has a standard deviation of 37.6, so you can expect that its performance will be roughly twice as volatile as the S&P 500. You can find a fund's beta and its standard deviation at www.morningstar.com.

*Don't go to cash. After taking a mauling from a bear market, many investors want to give up on stocks and bonds and move to money market mutual funds or bank CDs. But savings rates are so low that you'll earn close to nothing: The average money fund yields 0.05%, or $5 on a $10,000 deposit. Factor in inflation and taxes, and you'll earn less than nothing.

True, a 0.05% return is better than a big loss. But you have your best chance of getting back to even in stocks. Recovery time for a bear market depends on the severity of the downturn, says Jeff Hirsch, editor of the Stock Trader's Almanac. Hirsch thinks the market won't make new highs until 2011.

*Don't give up. Unless your retirement plan is to keel over at your desk, you need to lick your wounds and keep going. Even if you have a pension and Social Security, you'll need savings to maintain your standard of living.

How do you recover from the market's drubbing?

*Save more. The only sure-fire way to make up losses is to increase your savings. For example, suppose you earn $50,000 and contribute 5% of your salary to a 401(k) plan. You get 3% raises every year. If you earn 6% a year, you'll have $260,500 after 30 years.