At its height in 1992, Chiat Day had billings of $1.3 billion and 1,200 staff.
One of the agency's most famous campaigns was the "1984
spot for Apple Computers, which launched the Macintosh to the Superbowl-watching US public. It was lauded as "insanely great advertising
by the company's founder, Steven Jobs, but characterising Chiat Day's ability to lose big accounts as well as win them, Jobs pulled it from the business in 1986, although TBWA/Chiat/Day now holds the global account.
Other work included the Energizer Bunny and a campaign for Nike which involved blanketing Los Angeles with posters of athletes during the 1984 Olympics. It was so successful many thought Nike was the official Games sponsor - Converse had paid $4 million for the privilege.
Chiat is also credited with expanding the New York-centric ad industry to the west coast, as well as introducing account planning into US agencies.
MT Rainey, who set up Chiat Day in the UK and later founded Rainey Kelly Campbell Roalfe, said: "Jay was brilliant. The blueprint of his structure is still being followed by agencies trying to modernise."