Stocks are down sharply for a second day in a row, providing another reminder of how volatile the market has become.

The stock sell-off, which began in early October, has now wiped out all of the market's gains for the year. Yet stocks are still higher than they were at this time a year ago. 

Whatever happens to stocks now, average investors should use this as an opportunity to review their portfolio.

“If you’re a long-term investor, you should have a plan in place that expects that you’ll go through market corrections,” says Jeffrey DeMaso, director of research at Adviser Investments in Newton, Mass.

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This latest sell-off was partly triggered by big declines in leading tech companies like Apple and Facebook, as well as poor earnings reports from retail names like Target. In addition, investors are also feeling uncertainty over President Donald Trump’s trade policies and the aging bull market, which has slowed the flow of new money into stocks.

In September the current bull market stood as the longest in U.S. stock market history, at more than 9 years old. That raises concerns that it might not have much further to run.  (The longest bull market, which lasted through the 1990s, ended in early 2000 with the dot-com implosion and a 2½-year bear market.)

“This is definitely a mature market as well as a mature economy,” says James Stack, president of InvesTech Research in Whitefish, Mont., who tracks market history. “It’s time to be more defensive.”

Historical perspective might offer some comfort, but perhaps not in the face of this latest bout of rampant selling. So if you’ve lost faith in the bull market, consider these five investment strategies. 

1. Review Your Asset Mix

Chances are you haven’t updated your portfolio allocations lately. Few 401(k) investors make any changes after signing up. But what was right for you in your 20s or 30s may be too aggressive in your 40s or 50s, when your investing time horizon is much shorter.

To figure out what mix works for you now, test your risk tolerance. Say stocks plunged 50 percent, similar to what happened in the 2008 to 2009 bear market. If you hold 70 percent of your portfolio in stocks and 30 percent in bonds, that move might erase one-third of your portfolio. Perhaps you muddled through without panicking in the last financial crisis, but would you be able to hang on now? If you’re married, how would your spouse feel about these losses?

For those who would rather not see a rerun of that scenario—in particular, older investors and retirees—you would do well to shift a portion of your stocks into bonds for a tamer asset mix, says an investment adviser, William Bernstein, author of “The Four Pillars of Investing” (McGraw-Hill Education, 2010). Instead of a 70/30 stock-and-bond mix, opt for a 60/40 or 50/50 allocation instead, which would limit your losses. By scaling out of stocks, you will also be locking in some of your profits.

Still, younger investors who have the tenacity to ride out market declines should hang on to a more stock-heavy mix, Bernstein says. Over the long term, equities are likely to outperform other assets. 

2. Rebalance Your Portfolio

Choosing an asset mix does no good if you don’t maintain it through rebalancing. According to the investment firm Vanguard, someone who started in 2012 with a 60/40 stock-and-bond mix and failed to rebalance would have a 76/24 mix today, as a result of the big gains in stocks and modest returns on bonds.

Though the market correction may have already brought your portfolio closer to your original allocation, a better strategy is to rebalance, says Jim MacKay, a financial planner in Springfield, Mo. To do this, sell just enough of your winning investments and add that money to your laggards to bring your portfolio back to its original allocation or to the one that's right for you today.

“Rebalancing is counterintuitive, since you are selling your best performers and buying your worst performers, which is hard for most people to do,” says Francis Kinniry, a principal in Vanguard’s Investment Strategy Group. “But if you rebalance once a year or so, you typically find you only need to make small tweaks, perhaps shifting 2 percent of your portfolio.”

An even simpler strategy is to opt for an all-in-one fund, such as a target-date retirement fund, that automatically rebalances for you across a wide range of assets.  

3. Diversify Overseas

“Most investors have on blinders and only buy domestic stocks and avoid foreign stocks,” says Rob Arnott, founder and chairman of the investment firm Research Affiliates.

The U.S. accounts for only about 53 percent of the global stock market. But unless you are enrolled in a target-date fund, you probably hold little foreign stock. Only one-fifth of 401(k) savers hold an international stock fund if one is offered in their plan, Vanguard data show.

Granted, foreign stocks tend to be riskier than U.S. equities, especially shares of companies based in emerging markets. But overseas stocks are an important source of diversification because they don’t move in lockstep with U.S. stocks. They often zig when Wall Street zags, which can reduce risk over the long term.

That’s why you should consider stashing a portion of your equity stake in overseas stocks. As a benchmark, for someone planning to retire in 20 years, a typical 2040 target-date retirement fund holds 30 percent or more of its stock allocation in foreign equities. 

4. Focus on High-Quality Bonds

In September the Federal Reserve continued its program of slow, small interest-rate rises with another hike of 25 basis points. That puts pressure on bonds, which fall in price when rates rise. Since the start of the year, the iShares Core U.S. Aggregate Bond ETF (AGG), which tracks the overall U.S. fixed-income market, has dipped more than 4 percent.

Still, bonds remain an essential asset in your portfolio because they provide a cushion against the risk of stocks. So to hedge against rate hikes, opt for a diversified portfolio of bond funds, which hold short-, intermediate-, and longer-term issues, MacKay says. Over time you’ll earn most of the return of bonds with minimal volatility.

Be sure to stick with high-quality bonds—those that hold investment-grade and government issues. Vanguard analysis shows that lately investors have been flocking to lower-credit-quality issues, such as junk or below-investment-grade bonds, which may pay higher yields. But the risks of those issues closely mirror those of stocks. If the economy slows, low-quality bond holdings may take a big hit, along with your stock portfolio, Kinniry says.  

5. Step Up Your Saving

Although you may not be able to earn hefty returns in the coming years, there’s one key factor you can control—your savings rate, Bernstein says. Boosting the amount you stash away means you will be less dependent on high returns to reach your financial goals. And you don’t have to take a lot of risk to get there.

To make sure you save more, automate your contributions, starting with your 401(k) plan, and try to put away the max, which is $18,500 in 2018. (Those 50 and older can put away an additional $6,000.) For IRA investors, the max is $5,500; those 50 and older can contribute an additional $1,000.

Can’t save that much? Hike your contribution rate another percentage point or 2 for now and aim to increase it more in the future. And if you get a raise or receive a windfall, stash some or all of the money away. That way, your portfolio will stay on track whatever the market does.