Six months after announcing their intent to merge, global consulting giants Towers Perrin and Watson Wyatt have completed the union.

Following the Dec. 18, 2009, shareholder approval and receipt of regulatory authorizations, Watson Wyatt Chief Executive Officer John Haley will now lead the newly formed Towers Watson & Co. as chairman and chief executive officer, while Towers Perrin Chief Executive Officer Mark Mactas will serve as deputy chairman, president and chief operating officer.

The merger has created a “broader portfolio of services” for clients in an increasingly complex market, says Haley.

Towers Watson Class A common stock is now listed on both the New York Stock Exchange and NASDAQ under the ticker symbol TW. Based on the Dec. 31, 2009 closing price of discontinued Watson Wyatt common stock (WW), the implied value of the transaction is $4 billion.

The new firm will be headquartered in New York City. “Towers Watson builds on shared values of integrity, professional excellence and collaboration with a strong clients-first orientation,” says Mactas. “With our combined experience, and breadth and depth of skills, we will be able to provide greater insight as we work with our clients and greater opportunities for our people and our shareholders.”