Ernst & Young Global Limited, trade name EY, is a British multinational professional services partnership headquartered in London, England. EY is one of the largest professional services networks in the world. Along with Deloitte, KPMG, and PwC, it is considered one of the Big Four accounting firms. It primarily provides assurance (which includes financial audit), tax, consulting, and advisory services to its clients. EY operates as a network of member firms that are structured as separate legal entities in a partnership, which has 312,250 employees in over 700 offices in more than 150 countries around the world. The firm's current partnership was formed in 1989 by a merger of two accounting firms; Ernst & Whinney and Arthur Young & Co. It was named Ernst & Young until a rebranding campaign officially changed its name to EY in 2013, although this initialism was already used informally prior to its sanctioning adoption.