It was reported in 2004 that from 1988 through 2004 the fund returns averaged 29% a year.[1] His clients have included David Geffen (1988 - 2007),[7] Michael Dell, the Tisch family (owners of Loews Corporation), and the Ziff family (owners of Ziff Davis) (1988 - 2013).[3][7] In 2004, the fund made Lampert the first hedge fund manager ever to make more than $1 billion in a year, when the fund grew 69%, following his decision to buy Kmart and merge it with Sears.[8] At the start of the financial crisis of 2007–2010, however, ESL's retail holdings were severely affected due to a drop in consumer spending, and the company's investment in Citigroup in September 2007 saw a significant drop in value since the fund made its investment.[9] Through the fund, Lampert is worth approximately $2 billion.[4] Lampert, who typically invests in undervalued stocks, is known to have modeled his investing style on Warren Buffett's style by analyzing his annual shareholder letters.[2]