Why Pfizer Stock Tumbled on Tuesday

The specter of an activist investor looms over the company.Tuesday was a fairly eventful news day for U.S. pharmaceutical sector company Pfizer (PFE -1.39%). It reported third-quarter earnings and updated investors about its relationship with an activist investor in its ranks. Neither of these occurrences impressed the market, however, and the company's share price dipped by more than 1%. That was on a day when the S&P 500 index closed in the black, albeit modestly at 0.2%.Strong growth and twin beats weren ...