How to take advantage of a down market

You’ve heard the old saying about investing success: Buy low and sell high. It sounds easy, doesn’t it? The problem is, no one knows exactly where the peaks and valleys are until after the market has reached them. That’s why it’s important to have an investment plan and stick to it.

How can the average investor find success in buying low and selling high? Here’s the secret: continually contribute to a diversified portfolio and rebalance it when your portfolio’s allocation falls outside its target range.

The secret: dollar-cost averaging

Dollar-cost averaging is the key to a long-term investment strategy. It means contributing a set amount of money to your portfolio on a regular basis.

If you contribute to a 401(k) or 403(b) plan, you’re already doing this; every time you get paid, a certain percentage of your paycheck is deposited and immediately invested into your portfolio. There’s no consideration of market conditions. It doesn’t matter if the market is up or down; your money will get invested.

Here’s where the magic happens with dollar-cost averaging: When the market is down, it’s like getting your investments at a discount. You get to buy more shares of the same investment for less money.

Compare that to the alternative — a lump-sum portfolio, in which a larger sum is invested at one time, without regular additional contributions. With lump-sum investing, the available cash has already been invested, and taking advantage of sale prices becomes more difficult.

How do I benefit when the market recovers?

When you’re contributing regularly to your investment portfolio and purchasing shares at a discount during a bear market, you increase your upside potential when the market recovers.

When you take a lump sum of money and invest it, you initially have many more shares in a given investment than you would have if you spread those contributions out over a longer time. When the market declines, your lump-sum portfolio declines with it, but you’re not buying any additional shares at a discount like you are with your dollar-cost-averaged portfolio. You could end up with the same number of shares in both portfolios, but the average price per share in the dollar-cost-averaged portfolio will be lower.

This is why your 401(k) and 403(b) portfolios will seem to perform better than your lump-sum investment portfolio. In fact, they often do perform better because, over the long term, you end up purchasing your investment shares at a lower overall cost per share. So when the market recovers, you can be proud of yourself for buying at the bottom.

Stay invested for the long term

Dollar-cost averaging gives you an advantage over lump-sum investing, but in either case it’s important to stay the course and stay invested. Heading to the sidelines during market volatility greatly reduces your chances of long-term investment success.

The key phrase here is “long term.” If you are investing for the short term, market volatility is not your friend, and frankly, you probably shouldn’t be investing at all. Having a short-sighted view of the market causes many to abandon ship at the worst possible time and potentially end up buying high and selling low — the exact opposite of what you should be doing.

If you do have a lump-sum investment portfolio, don’t fear. You can still take advantage of market downturns by rebalancing your portfolio. What this means is that you move money out of the best-performing asset classes — whether they be stocks, bonds or Treasuries — and into the underperforming asset classes. This allows you to maintain your target asset allocation and helps you avoid being “overweighted” in an asset class that has performed well but may decline in the future. This is the essence of buying low and selling high.

Be the tortoise

Although market downturns are no fun, they’re inevitable. The reason you have the potential to receive higher rates of return on your investments is because you take on the risk of losing money.

The best advice is to be the tortoise, not the hare. When you’re in the accumulation stage and building your nest egg, practice a slow and steady approach to investing. Stay the course, no matter what the markets are doing.

On the other hand, during the de-accumulation stage of your portfolio, you may need to minimize your exposure to equities to protect yourself from not having the money when you need it. Most importantly, during this stage, make sure your retirement income plan accounts for the inevitability of market downturns — and follow through on that plan.

I hope this gives you the confidence you need to stick to your investment plan no matter what is happening in the markets. If you don’t have a plan, start building one and set the goal of seeing it through.

Scott Weiss is the director of financial planning at Weiss Financial Group in Mahopac, N.Y. Learn more about Scott at NerdWallet's 'Ask an Advisor.' This article first appeared at NerdWallet.