Trading on dozens of major public companies, including Apple Inc. (NASDAQ:AAPL), Google Inc (NASDAQ:GOOG) and Facebook Inc (NASDAQ:FB) was halted shortly after midday due to a technical glitch reported by NASDAQ OMX Group, Inc. (NASDAQ:NDAQ). Many of the stocks affected are among the most-traded, and as the outage approached an hour in length, it became clear that major stock indexes are going to be affected.


Indexes affected by halted trading

Approximately 3,200 companies have their listings on the NASDAQ, and statistics from BATS Global Markets indicates that approximately 28 percent of shares traded this month so far were stocks listed on the NASDAQ. MarketWatch contributor Tom Bemis of The Tell estimates that the total market capitalization of all the companies affected by the outage was about $5.7 trillion.

Of course today’s outage means that the NASDAQ Composite Index wasn’t being updated, and this may be the first time in the index’s history that this has ever happened. Also the Dow Jones Industrial Average and the S&P 500 are sure to be skewed by today’s outage.

Microsoft Corporation (NASDAQ:MSFT) was one of the companies pulling the Dow Jones higher on Thursday before trading was halted on the NASDAQ. Now the stock is dead in the water until NASDAQ OMX Group, Inc. (NASDAQ:NDAQ) fixes the glitch. Apple Inc. (NASDAQ:AAPL) alone, with its sizeable heft, has the ability to pull down or drag up the S&P 500, and with trading on Apple shares halted, the index will likely be extremely skewed.

Global markets affected by NASDAQ outage

With investors not being able to trade these popular stocks, ripples could begin going throughout the global markets. Traders at multiple firms feel essentially stuck because they are unable to trade some of the most popular stocks on the market. Options trading has also been affected as NYSE Euronext, the parent company of the New York Stock Exchange, has halted call trading in NASDAQ-listed shares per a request from NASDAQ.

At this point the Securities and Exchange Commission says it is monitoring the outage and talking with the stock exchanges.