Stocks, bonds and commodities all fared poorly in 2018

"For the first time in decades, every major type of investment has fared poorly, as the outlook for economic growth and corporate profits is dampened by rising trade tensions and interest rates," the N.Y. Times' Matt Phillips writes.

Why it matters: "Most years, financial markets are a mixed bag. A bad year for risky investments, like stocks, might be a great one for safe bets like government bonds. Or, if worries about inflation are hurting bond investments, commodities like gold tend to do well." But now, stocks "around the world are getting pummeled, while commodities and bonds are tumbling — all of which have left investors with few places to put their money."

Be smart: "If this persists, or grows worse, it could create a damaging feedback loop, with doubts about the economy hurting the markets, and trouble in the markets undermining growth."

Go deeper: 3 warning signs U.S. economy could be close to recession