He presumably would have done so by relying on a special IRS "safe harbor" rule relating to the taxation of a service partner's receipt of such interests, but that rule emphatically does not apply to an interest when sold to a retirement plan, which is supposed to be measured by its true fair market value.

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At the heart of Buffett's simple but highly effective strategy is having the discipline to recognize when the market is not properly reflecting the true long-term value of a particular business, which can be calculated by discounting its likely future cash flows at an appropriate discount rate.

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But it remains true that the symbolic value of sanctions is lost if America's policy is criticised by its own allies, and their economic impact is lost if other countries do the deals that America withdraws from.

ECONOMIST: The many-handed Mr Eizenstat