the allowance is adjusted accordingly. The allowance for trade receivable is $21.7 million and $18.2 million as of December 31, 2010 and 2009. The provision to the allowance for trade receivables charged against continuing operations was $4.3 million, $5.8 million and $3.1 million for the years ended December 31, 2010, 2009 and 2008, respectively. 

## investments 

Investments in companies in which our ownership interest is 50 percent or less and in which we exercise significant influence over operating and financial policies are accounted for using the equity method. Under the equity method, original investments are recorded at cost and adjusted by our share of undistributed earnings and losses of these investments. Majority owned investments in which our control is restricted are also accounted for using the equity method. All other investments are carried at their fair values or at cost, as appropriate. We are party to several joint venture investments throughout the world, which individually and in the aggregate are not significant to our financial results. 

## inventories 

Inventories are stated at the lower of cost or market value. Inventory costs include those costs directly attributable to products before sale, including all manufacturing overhead but excluding distribution costs. All domestic inventories, excluding materials and supplies, are determined on a last-in, first-out (“LIFO”) basis and our remaining inventories are recorded on a first-in, first-out (“FIFO”) basis. See Note 5. 

## property, plant and equipment 

We record property, plant and equipment, including capitalized interest, at cost. Depreciation is provided principally on the straight-line basis over the estimated useful lives of the assets (land improvements — 20 years, buildings — 20 to 40 years, and machinery and equipment — 3 to 18 years). Gains and losses are reflected in income upon sale or retirement of assets. Expenditures that extend the useful lives of property, plant and equipment or increase productivity are capitalized. Ordinary repairs and maintenance are expensed as incurred through operating expense. 

## impairments of long-lived assets 

We review the recovery of the net book value of long-lived assets whenever events and circumstances indicate that the net book value of an asset may not be recoverable from the estimated undiscounted future cash flows expected to result from its use and eventual disposition. In cases where undiscounted expected future cash flows are less than the net book value, we recognize an impairment loss equal to an amount by which the net book value exceeds the fair value of the asset. Long-lived assets to be disposed of are reported at the lower of carrying amount or fair value less cost to sell. 

## asset retirement obligations 

We record asset retirement obligations at fair value at the time the liability is incurred if we can reasonably estimate the settlement date. The associated asset retirement obligations (“AROs”) are capitalized as part of the carrying amount of related long-lived assets. In future periods, the liability is accreted to its present value and the capitalized cost is depreciated over the useful life of the related asset. We also adjust the liability for changes resulting from the passage of time and/or revisions to the timing or the amount of 

the original estimate. Upon retirement of the long-lived asset, we either settle the obligation for its recorded amount or incur a gain or loss. See Note 8 for further discussion on our AROs. 

## restructuring and other charges 

We continually perform strategic reviews and assess the return on our businesses. This sometimes results in a plan to restructure the operations of a business. We record an accrual for severance and other exit costs under the provisions of the relevant accounting guidance. 

Additionally, as part of these restructuring plans, write-downs of long-lived assets may occur. Two types of assets are impacted: assets to be disposed of by sale and assets to be abandoned. Assets to be disposed of by sale are measured at the lower of carrying amount or estimated net proceeds from the sale. Assets to be abandoned with no remaining future service potential are written down to amounts expected to be recovered. The useful life of assets to be abandoned that have a remaining future service potential are adjusted and accelerated depreciation is recorded over the adjusted useful life. 

## Capitalized interest 

We capitalized interest costs of $7.5 million in 2010, $3.8 million in 2009 and $5.7 million in 2008. These costs were associated with the construction of certain long-lived assets and have been capitalized as part of the cost of those assets. We amortize capitalized interest over the assets’ estimated useful lives. 

## other assets 

Unamortized capitalized software costs totaling $18.5 million and $13.8 million at December 31, 2010 and 2009, respectively, are components of other assets, which also include debt financing fees, advances to contract manufacturers, recoveries related to environmental obligations (see Note 10), intangibles assets other than goodwill (see Note 4), fair value of a deferred compensation arrangement (see Note 17) and other deferred charges. We capitalize the costs of internal use software in accordance with accounting literature which generally requires the capitalization of certain costs incurred to develop or obtain internal use software. We assess the recoverability of capitalized software costs on an ongoing basis and record write-downs to fair value as necessary. We amortize capitalized software costs over expected useful lives ranging from three to ten years. 

## goodwill and intangible assets 

Goodwill and other indefinite life intangible assets (“intangibles”) are not subject to amortization. Instead, they are subject to at least an annual assessment for impairment by applying a fair value-based test. 

We test goodwill for impairment annually using the criteria prescribed by U.S. GAAP accounting guidance for goodwill and other intangible assets. We did not record any goodwill impairments in 2010, 2009 and 2008. Based upon our annual impairment test, conducted in 2010, we believe that the fair value of our reporting units with goodwill substantially exceeds their carrying value. 

Definite life intangible assets consist primarily of patents, access rights, customer relationships, registration rights, industry licenses, developed formulations and other intangibles and are being amortized over periods of 5 to 20 years. See Note 4 for additional information on goodwill and intangible assets. 

