High-profile proponents of value investing, including Berkshire Hathaway chairman Warren Buffett, have argued that the essence of value investing is buying stocks at less than their intrinsic value. The discount of the market price to the intrinsic value is what Benjamin Graham called the "margin of safety". For the last 25 years, under the influence of Charlie Munger, Buffett expanded the value investing concept with a focus on "finding an outstanding company at a sensible price" rather than generic companies at a bargain price. Hedge fund manager Seth Klarman has described value investing as rooted in a rejection of the efficient market hypothesis (EMH). While the EMH proposes that securities are accurately priced based on all available data, value investing proposes that some equities are not accurately priced.