We review all of our intangible assets for impairment at least annually and whenever events or changes in business circumstances indicate that the carrying value of the assets may not be recoverable. We perform these impairment reviews at the reporting unit level with respect to goodwill and at the business unit level for amortizable intangible assets. In reviewing intangible assets, if the fair value were less than the carrying amount of the respective (or underlying) asset, an indicator of impairment would exist and further analysis would be required to determine whether or not a loss would need to be charged against current period earnings. Based on the results of impairment reviews in 2014, 2013 and 2012, we wrote off $1.8 million, $2.2 million and $3.5 million, respectively, of amortizable intangible assets primarily related to prior year acquisitions in our brokerage segment. The determinations of impairment indicators and fair value are based on estimates and assumptions related to the amount and timing of future cash flows and future interest rates. Different estimates or assumptions could produce different results.
In the discussion that follows regarding our results of operations, we also provide the following ratios with respect to our operating results: pretax profit margin, compensation expense ratio and operating expense ratio. Pretax profit margin represents pretax earnings divided by total revenues. The compensation expense ratio is compensation expense divided by total revenues. The operating expense ratio is operating expense divided by total revenues.
The increase in salary and benefit expenses in 2014 compared to 2013 was primarily due to a $12.0 million charge related to the de-risking strategy of our U.S. defined benefit plan, offset by a reduction in pension expense of $3.6 million. In the period from September 12, 2014 to November 30, 2014, we offered a one-time voluntary lump sum window to eligible deferred vested participants in our U.S. defined benefit plan in an effort to reduce our long-term pension obligations and the volatility of these obligations on our balance sheet. The aggregate lump sum payout made in fourth quarter 2014 was $43.3 million. This lump sum payout project reduced the plan’s pension benefit obligation by approximately $60.0 million, while improving its pension underfunding by almost $17.0 million as of December 31, 2014. Due to this significant obligation settlement, we incurred a non-cash pre-tax charge of approximately $12.0 million in fourth quarter 2014, as a result of the U.S. GAAP requirement to expense the portion of the unrealized actuarial losses currently recognized as accumulated other comprehensive loss, based on a ratio of the liability settled to the total liability within the plan at December 31, 2014. The increase in salary and benefit expenses in 2013 compared to 2012 was primarily due to additional headcount and salary and benefits expense increases.
Interest expense - The increase in interest expense in 2014 compared to 2013 and 2013 compared to 2012 was due to the following:
Interest and banking costs includes expenses related to our debt. Clean energy investments include the operating results related to our investments in clean coal production plants and Chem-Mod. Acquisition costs include professional fees, due diligence and other costs incurred related to our acquisitions. In 2013, acquisition costs include a gain of $2.6 million on the derivative investment contract discussed above. Corporate consists of overhead allocations mostly related to corporate staff compensation and, in 2014 and 2013, costs related to biannual company-wide award, cross-selling and motivational meetings for our production staff and field management
Our investment in Chem-Mod generates royalty income from refined coal production plants owned by those limited liability companies in which we invest as well as refined coal production plants owned by other unrelated parties. Based on current production estimates provided by licensees, Chem-Mod could generate for us an average of approximately $4.0 million of net after-tax earnings per quarter.
(1) The IRS will not release the factors for 2015 until April or May 2015. Based on our analysis of the factors used in the IRS’ phase out calculations, it is our belief that there will be no phase out in 2015.
The changes in the carrying amount of goodwill for 2014 and 2013 are as follows (in millions):
The interest rates on Facility B are Interbank rates, which vary by tranche, duration and currency, plus a margin of 1.65%. The interest rates on Facilities C and D are 30 day Interbank rates, plus a margin of 0.85%. The annual fee for Facility B is 0.7425% of the undrawn commitments for the two tranches of the facility. The annual fee for Facilities C and D is 0.80% of the total commitments of the facilities. In connection with entering into the Premium Financing Debt Facility, we incurred an upfront fee of 0.30% of the principal amount of the committed facilities.
We believe that the application of The Chem-Mod™ Solution qualifies for refined coal tax credits under IRC Section 45 when used with refined coal production plants placed in service by December 31, 2011 or 2009. Chem-Mod has been marketing its technologies principally to coal-fired power plants owned by utility companies, including those utilities that are operating with the IRC Section 45 refined coal production plants in which we hold an investment.
Chem-Mod is determined to be a variable interest entity (which we refer to as a VIE). We are the controlling manager of Chem-Mod and therefore consolidate its operations into our consolidated financial statements. At December 31, 2014, total assets and total liabilities of this VIE included in our consolidated balance sheet were $10.2 million and $1.2 million, respectively. For 2014, total revenues and expenses were $69.1 million and $38.4 million (including non-controlling interest of $35.3 million), respectively. We are under no obligation to fund Chem-Mod’s operations in the future.