Instead of worrying about the wider world, investors focused on the Federal Reserve and the outlook for its stimulus program.
The Fed bought $85 billion in government bonds each month in 2013. The purchases were designed to hold down long-term borrowing rates and encourage spending and investment. The stimulus also prodded investors to move from low-yielding bonds to stocks.
Investors reacted to every twist and turn of the program's fate. They sold stocks in the spring and summer over fears the central bank would slow its bond-buying prematurely. They worried that every bit of good economic news signaled the end of support. But in December, as hiring grew consistently stronger, investors were confident enough in the economy that they reacted positively when Fed officials finally decided to dial back purchases. The Fed also reassured the market by signaling it would keep short-term rates near zero. The stock market, which had hovered below all-time highs, returned to record territory.
Of course, it wasn't all about the Fed. Companies also played a part.
Despite a middling economy, U.S. corporate earnings rose for a fourth straight year. Total earnings for S&P 500 companies in 2013 are forecast to increase 5.37 percent to a record $109.03 a share, according to data from S&P Capital IQ.
"It's tough to argue that companies are in anything other than good health," says Paul Atkinson, head of North American equities at Aberdeen Asset Management, a global fund management company that oversees about $325 billion.
Investors, emboldened by the Fed's support and low inflation, were willing to pay more for those earnings. The price-earnings ratio for the S&P 500 index, a measure of earnings compared with stock prices, rose to 15.4 from 12.6 at the start of 2013, according to FactSet data. By that measure, stocks grew more expensive, but weren't necessarily overvalued. The P/E ratio remained below its 20-year average of 16.5.
Here are 10 lessons from the year of the bull:
SMALL COMPANIES CAN GIVE BIG RETURNS
Some of the best performers of the year weren't the big blue-chip stocks, but smaller ones. The Russell 2000, an index that tracks small stocks, rose 37 percent, more than the Dow and the S&P 500. Smaller companies are more focused on the United States than larger multi-national corporations. That means they benefit more when the U.S. grows faster than other parts of the world, such as Europe. That's exactly what happened in 2013.
THE BOND PARTY IS OVER
Yes, they were safe, but with 10-year Treasury notes paying interest below 3 percent for most of the year, bonds weren't sexy. From 1981 to 2012, government and company bonds rose 35 percent, according to the Barclays Capital U.S. Aggregate Bond Index, a broad measure of the debt market. In 2013, bonds in the index handed investors a loss of 2 percent, the first since 1999.
As the economy improves, many investors believe that interest rates will continue to rise and bonds will only fall further.