Seth Klarman’s extraordinary and mysterious book Margin of Safety, Risk Averse Investing Strategies for the Thoughtful Investor has sold for $700 for used varieties with newer copies going for $2,500 to $4,000. His foremost investing premise is risk mitigation. He writes,

It follows that value investors seek a margin of safety, allowing room for imprecision, bad luck, or analytical error in order to avoid sizable losses over time. A margin of safety is necessary because valuation is an imprecise art, the future is unpredictable, and investors are human and do make mistakes. It is adherence to the concept of a margin of safety that best distinguishes value investors from all others, who are not as concerned about loss.

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The most beneficial time to be a value investor is when the market is falling. This is when downside risk matters and when investors who worried only about what could go right suffer the consequences of undue optimism. Value investors invest with a margin of safety that protects them from large losses in declining markets.