The retention of business produced in the Standard Commercial Segment that was previously retained by third parties also contributed $48.3 million to the increase in revenue, but was partially offset by lower ceding commission revenue of $15.7 million and lower processing and service fees of $2.7 million primarily attributable to the shift from a third-party agency structure to an insurance underwriting structure. Earned premium from the Personal Segment contributed $4.9 million and additional finance charges contributed $0.4 million to the increase in revenue, but were partially offset by lower ceding commission revenue of $1.8 million and lower processing and service fees of $0.3 million attributable to increased retention of the policies produced. The investment of funds derived from the implementation of our 2005 capital plan and a trust account to secure the future guaranteed payments to the sellers of acquired subsidiaries contributed another $3.4 million to revenue for fiscal 2006 as compared to fiscal 2005. These increases were partially offset by realized losses on our investment portfolio of $1.5 million in 2006.
Net expense ratio is calculated as total underwriting expenses of our insurance company subsidiaries, including allocated overhead expenses and offset by agency fee income, divided by net premiums earned, each determined in accordance with GAAP. During the fourth quarter of fiscal 2006, we adopted the widely used industry calculation that offsets expenses with agency fee income. All prior period comparative expense ratios have been restated.
Corporate pre-tax loss was $20.5 million for the year ended December 31, 2006 as compared to $4.8 million for the prior year. The increased pre-tax loss was primarily due to $9.6 million in interest expense from amortization attributable to the deemed discount on convertible promissory notes issued in January, 2006. This interest expense had no impact on our cash flow or book value. Also contributing to the increased corporate pre-tax loss was additional interest expense of $4.3 million comprised of: (i) $1.1 million from the trust preferred securities issued in the second quarter of 2005 (see Note 7, "Notes Payable"); (ii) $1.1 million of amortization of the discount on the future guaranteed payments to the sellers of acquired subsidiaries (see Note 8, "Structured Settlements"); (iii) $1.0 million from a related party promissory note issued in January 2006; (iv) $0.8 million from borrowings under our revolving credit facility in January 2006 (see Note 7, "Notes Payable" and Note 9, "Credit Facilities"); and (v) $0.3 million from the convertible notes issued in January 2006. Also contributing to the increase in pre-tax loss was increased salary and related expenses of $0.9 million, professional services of $0.4 million, decreased revenue discussed above and travel expenses of $0.2 million.
Net expense ratio is calculated as total underwriting expenses of our insurance company subsidiaries, including allocated overhead expenses and offset by agency fee income, divided by net premiums earned, each determined in accordance with GAAP. During the fourth quarter of fiscal 2006, we adopted the widely used industry calculation that offsets expenses with agency fee income. All prior period comparative expense ratios have been restated.
Total revenue for the Standard Commercial Segment of $43.1 million for 2005 was $19.5 million more than the $23.6 million reported in 2004. This 82.8% increase in total revenue was primarily due to net premiums earned of $21.8 million from the issuance of AHIC policies and the assumption of premium from Clarendon for business produced by this segment. Increased net investment income contributed $1.5 million to the increase in revenue. These increases in revenue were partially offset by lower ceding commission revenue of $3.2 million and lower processing and service fees of $0.6 million, in both cases due to the shift from a third-party agency structure to an insurance underwriting structure. Total earned premium generated by the Standard Commercial Segment for 2005, including premium retained by Clarendon, was $78.1 million as compared to $72.5 million for 2004.