Apple's fourth-quarter earnings results Wednesday night disappointed investors and the stock was down more than 10% in trading Thursday morning. According to 13F filings, pension funds directly hold 3.67% of the outstanding float. Based on Thursday's movement of the stock, that translates to a paper loss of $1.8 billion, not to mention any exposure to the stock that pension funds might have through funds overseen by external managers. From the stock's high in September through Thursday, the market value of pension funds' direct Apple holdings has fallen more than $8.2 billion.