Einhorn's fund was only up 8.3% in 2012 while the S&P was up 13.4% in the same period.
Coming into December, Einhorn's fund was up double digits but a rough December saw his fund lose 2.8% in December.
Specifically, Einhorn watched gains in Apple (AAPL) disappear during the month of December. Apple was a huge part of Einhorn's portfolio at over 13%. Apple shares were hit hard amid fears of a slowdown in sales for the iPhone 5.
In addition, Einhorn had a big bet on gold in 2012 that produced only small gains. As of last quarter, 5.3% of his portfolio was in the gold ETF (GDX). Gold had a rough December with rumors that John Paulson was selling to meet liquidation orders.