Matt Krantz, USA TODAY
Facebook, the No. 1 social networking company, gained even more status with investors Wednesday after being added to the popular Standard & Poor's 500 index.
The company, which sold shares to the public for the first time in 2012, is replacing Teradyne in the much-followed S&P 500.
Facebook is also replacing The Williams Cos. in the S&P 100 index of the very largest U.S. companies.
The changes go into effect after the close of trading Dec. 20.
Shares of Facebook jumped 4% in after-hours trading on the news. Facebook fell 87 cents, or 1.7%, to close at $49.38 in regular trading.