(3) Book value per share is calculated by dividing the sum of shares outstanding plus contractually issuable shares into total shareholders' equity.
In conjunction with the expansion of underwriting activities by our insurance companies and in an effort to increase the efficiency of certain of our operations, we consolidated the operations of certain of our agency operations with those of certain of our insurance companies in 2001 and 2002. These consolidations will result
Net investment income was $39.6 million for 2001 compared to $39.8 million in 2000. The positive effect on investment income of our higher level of invested assets was offset by a significant decrease in interest rates in 2001. We expect positive operating cash flow to continue in 2002, thereby increasing invested assets and investment income, but the increase could again be substantially offset by the effect of continued low interest rates. During 2001, we recorded a net realized investment gain of $0.4 million, compared to a loss of $5.3 million in 2000. During 2001 we recognized a $2.4 million realized loss from the write down of five investments to their estimated fair market value compared to a similar write down of $5.1 million from one equity investment during 2000. The loss from write downs during 2001 was offset by other gains recorded on investments sold.
Net earnings before the change in accounting was $30.2 million, or $0.51 per diluted share, for 2001 compared to $57.5 million, or $1.11 per diluted share, in 2000. This decrease primarily results from the after tax loss from the September 11 terrorist attacks of $22.8 million, or $0.38 per diluted share, and the after tax charge for lines of business being exited of $29.6 million, or $0.50 per diluted share.
In 2000, we engaged General Re New England Asset Management, a subsidiary of Berkshire Hathaway, Inc. and a nationally prominent investment advisor, particularly to insurance companies, and undertook an in-depth review and restructuring of our investment portfolio. As a part of this restructuring, we shortened our investment portfolio's duration but did not significantly change the average credit rating. Our net realized investment losses from sales or write downs of equity securities was $5.6 million in 2000, compared to losses of $3.9 million in 1999. In 2000, we recognized a $5.1 million realized loss from the write down of an equity investment to its estimated fair market value based upon market quotations compared to a similar write down
Our income tax expense was $35.9 million in 2000 compared to $12.3 million in 1999. Our effective tax rate was 39% in the 2000 period compared to 32% in 1999. Most of the increase in the effective tax rate was due to non-deductible goodwill amortization relating to The Centris Group, Inc. acquisition, a shift of fixed income investments to taxable instruments from tax exempt instruments and increased underwriting agency income which is subject to state income taxes.
Commission income decreased to $49.9 million in 2000 from $58.2 million in 1999. Net earnings of our intermediaries decreased to $11.2 million in 2000 from $15.1 million in 1999. These decreases were due to a significant reduction in the amount of ceded reinsurance placed on behalf of our insurance companies as a result of their planned increase in retentions.
foreign currency exchange risk of the recurring monthly expenses. We utilize these foreign currency forward contracts strictly as a hedge against existing exposure to foreign currency fluctuations rather than as a form of speculative or trading investment. The fair value of foreign currency forward contracts December 31, 2001 was immaterial.
SFAS No. 142 also requires the discontinuance of the amortization of goodwill effective January 1, 2002 and that goodwill recognized for acquisition which were consummated after July 1, 2001 not be amortized. Amortization of goodwill charged to operations, net of tax effect, in 2001, 2000 and 1999 was $11.0 million, $11.5 million and $5.5 million, respectively. We did not amortize the goodwill related to our acquisitions consummated in October, 2001.