Standard & Poor’s on Wednesday said that the social networking giant, Facebook, will be joining its S&P 500 and S&P 100 stock indexes after close of trading on Dec. 20, more than a year after its stormy initial public offering.

Facebook's entry to the S&P 500 index could help boost the company's stock, which is steadily recovering from a rocky start and a subsequent drop in price after its much-hyped, and controversial, IPO in May 2012. The move also means investors and mutual fund companies that track the index will begin adding Facebook to their holdings.

Facebook shares ended down 86 cents, or 1.7 percent, at $49.38 on Wednesday, but rose more than 4 percent in after-hours trading after the S&P announcement. The Menlo Park, Calif.-based company will replace testing-equipment maker Teradyne (NYSE:TER) on the S&P 500 and Williams Companies Inc. (NYSE:WMB) on the S&P 100 stock index of large U.S. companies.

Facebook’s entry to the S&P 500 index was widely anticipated after the company reported its fourth straight quarterly profit in October, a pre-requisite for entering the index. After its initial offering at $38 a share in May 2012, Facebook's shares lost half their value in the following months. However, the stock recovered from lows this year as the company's advertising business began generating revenues, mainly aided by its mobile devices-based advertising business.

Facebook posted a profit of $425 million during the third quarter, reversing a loss in the same period last year. And, the company's shares have soared 86 percent this year, about 30 percent above their initial offering price, and the company had a market value of $121.2 billion at close of trading on Wednesday, making it the thirtieth-most valuable company on the S&P 500 index.

S&P, in a release, also said that Teradyne will replace Scholastic Corp. (NASDAQ: SCHL) in the S&P MidCap 400, and Scholastic will replace Lincoln Education Services Corp. (NASDAQ:LINC) in the S&P SmallCap 600. Williams Companies Inc. will remain in the S&P 500.

Other changes to the indexes include: S&P MidCap 400 constituents Alliance Data Systems Corp. (NYSE:ADS) and Mohawk Industries Inc. (NYSE:MHK) will replace Abercrombie & Fitch Co. (NYSE:ANF) and JDS Uniphase Corp. (NASDAQ:JDSU) in the S&P 500. Abercrombie & Fitch and JDS Uniphase will replace Alliance Data Systems and Mohawk Industries in the S&P MidCap 400.  

S&P SmallCap 600 constituents Old Dominion Freight Line Inc. (NASDAQ:ODFL) and Brunswick Corp. (NYSE:BC) will replace Arch Coal Inc. (NYSE:ACI) and Regis Corp. (NYSE:RGS) in the S&P MidCap 400, while Arch Coal and Regis will replace Old Dominion Freight Line and Brunswick in the S&P SmallCap 600.