David Einhorn just posted his best quarter ever. Here's what's working for him

David Einhorn, founder of Greenlight Capital.
Adam Jeffery | CNBC

David Einhorn's Greenlight Capital ended a rough year on a high note, using a record-breaking fourth quarter to post a positive return for the year.

Einhorn's funds gained 25% in the fourth quarter as the company's long positions, including some bets on newly public companies, offset a weak period for the Greenlight's short positions, according to an investor letter obtained by CNBC.

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