'Quadruple Witching' casts spell on Dow

Less than an hour after opening, the index had climbed more than 41 points, or 0.47%, to 8,596. Quadruple Witching day is one on which contracts for stock index futures, stock index options, stock options and single stock futures all expire. Traditionally, stocks push higher during the expirations. Shares also continued to benefit from unexpectedly positive economic data published yesterday by both the Labor Department and the Philadelphia Fed index, which examines regional manufacturing trends. Aluminium producer Alcoa was among the biggest winners, gaining $0.35, or 3.25%, to $11.13...