This decade has the potential to go down in history as one of the worst for our economy and exchange traded funds (ETFs).

Today the Dow Jones and S&P 500 extended their declines, and now the major indexes are trading at or near four-year lows. The Federal Reserve’s plan to buy commercial paper didn’t restore market confidence, says Kate Gibson for MarketWatch.

Federal Reserve Chairman Ben Bernanke hinted today the the economy could get worse, and also signaled that the Fed might be cutting interest rates, reports Chris Isidore for CNN Money. The next scheduled meeting will take place Oct. 28-29, but some economists think an emergency meeting could take place before then.

Ron Surz for Advisor Perspectives says that unless things turn around within the next 15 months, the 2000s will forever be remembered as a lost decade, with the markets losing money for the first time.

Surz notes that while this economy has been a challenge for everyone, we can still make the best of it and use the experience to grow. After all, these markets will turn around someday, but we can’t forget what happened.

Look at the chart below, which shows that even the 1930s, marred by the Great Depression, managed to end flat.

On average this decade, the S&P has lost 1% a year. In fact, Surz says, investors probably would have been better off in bonds or Treasury bills than stocks. It makes many wonder what actually is safe.

One place investors could have come out ahead is in foreign markets, which returned more than 6% per year until recently.

But just because the 2000s might wind up being a loss overall, there are still lessons to take away. For one, this kind of period is a great way to “stress test” those investments meant to be good defensive plays. How are they really holding up? It’s a good way to see how your professional investment managers do, too. What sectors and styles have done well, and which haven’t?

While the year is almost over and we’re down right now, we’re never completely out if we can recognize and use the valuable lessons in the future.