Looking at options trading activity among components of the S&P 500 index, there is noteworthy activity today in Microsoft Corporation (MSFT), where a total volume of 122,723 contracts has been traded thus far today, a contract volume which is representative of approximately 12.3 million underlying shares (given that every 1 contract represents 100 underlying shares). That number works out to 49.9% of MSFT's average daily trading volume over the past month, of 24.6 million shares..