Note 4: Property, Plant and Equipment and Intangible Assets

Property, plant and equipment is recorded at historical cost. Depreciation and amortization are recognized on a straight-line basis over an asset's estimated useful life. Land is not depreciated and construction in progress is not depreciated until ready for service. Amortization of intangible assets for each of the next five years, based on existing intangible assets as of December 31, 2011 and using average 2011 foreign exchange rates, is expected to be $122 million in 2012, $113 million in 2013, $98 million in 2014, $89 million in 2015 and $81 million in 2016.

Depreciable and amortizable assets are only evaluated for impairment upon a significant change in the operating or macroeconomic environment. In these circumstances, if an evaluation of the undiscounted cash flows indicates impairment, the asset is written down to its estimated fair value, which is based on discounted future cash flows. Useful lives are periodically evaluated to determine whether events or circumstances have occurred which indicate the need for revision. For additional unaudited information on our policies for amortizable brands, see "Our Critical Accounting Policies" in Management's Discussion and Analysis.

Nonamortizable Intangible Assets

Perpetual brands and goodwill are assessed for impairment at least annually. If the carrying amount of a perpetual brand exceeds its fair value, as determined by its discounted cash flows, an impairment loss is recognized in an amount equal to that excess. We did not recognize any impairment charges for goodwill in the years presented. In connection with the merger and integration of WBD in 2011, we recorded a $14 million impairment charge for discontinued brands. We did not recognize any impairment charges for other nonamortizable intangible assets in 2010. The change in the book value of nonamortizable intangible assets is as follows:

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