In connection with OneBeacon's initial public offering, options were issued to certain key employees as a one-time incentive. The options did not include a mechanism to reflect the contribution to total return from the regular quarterly dividend. As a result, in February 2008, the Compensation Committee approved a grant of restricted stock units as a supplement to the initial public offering stock grant. The performance goal for the restricted stock units is growth in adjusted book value per share. As of December 31, 2009, 93,610 restricted stock units were outstanding.
Our total pre-tax investment results were $374.1 million, a return of 9.9% for the year ended December 31, 2009, compared to $(599.2) million, a return of (13.0)%, for the year ended December 31, 2008. Net investment income in the year ended December 31, 2009 was $125.5 million, a decrease of $38.9 million, compared to $164.4 million in the year ended December 31, 2008. The decrease was due to a lower average invested asset base and lower investment yields. Contributing to the lower investment yields was a $(1.1) million inflation adjustment related to our inflation indexed treasury securities for the year ended December 31, 2009 as compared to an $8.6 million inflation adjustment related to these securities for the year ended December 31, 2008. Net investment income in the year ended December 31, 2008 included $6.2 million related to assets held in trust. Net realized investment (losses) gains were $(20.5) million in the year ended December 31, 2009, an increase of $298.4 million, compared to $(318.9) million in the year ended December 31, 2008. The change in net unrealized investment gains and losses resulted in a gain of $269.1 million in the year ended December 31, 2009, compared to a loss of $444.7 million in the year ended December 31, 2008. As described above, net realized and unrealized investment losses experienced in 2008 resulted from the crisis that occurred in the financial markets during the third and fourth quarters of 2008.
Prior to February 2009, the collateral was controlled by the lending agent. The lending agent managed the investment of the cash collateral, however, other than in the event of default by the borrower, this collateral was not available to us and was remitted to the borrower by the lending agent upon the return of the loaned securities. Because of these restrictions, we considered our securities
The balances included in the table above regarding our long-term incentive compensation plans include amounts payable for performance shares and units, as well as deferred compensation balances. Exact amounts to be paid cannot be predicted with certainty as the ultimate amounts of these liabilities are based on future performance. The estimated payments reflected in the table are based on current accrual factors (common share price and pay-out percentage) and assume that all outstanding balances were 100% vested as of December 31, 2009.
On August 22, 2007, our Board of Directors authorized us to repurchase up to $200.0 million of OneBeacon's Class A common shares from time to time, subject to market conditions. Shares may be repurchased on the open market or through privately negotiated transactions. This program does not have a stated expiration date. During the year ended December 31, 2009, no shares were repurchased. During the year ended December 31, 2008, 3.4 million Class A common shares were repurchased for $68.8 million and retired.