The carrying values are based on external appraisals that are completed annually as of December 31. The appraisals utilize  a combination of the discounted cash flow and sales comparison approaches to arrive at the estimated value. The significant  unobservable inputs (level 3) included in the discounted cash flow models used when determining the fair value of standing  timber and agricultural assets include: Key valuation assumptions include a weighted average discount and terminal capitalization rate of 6.9% (2012 – 6.2%),  and terminal valuation dates of 20 to 28 years (2012 – 20 to 90 years). Timber and agricultural asset prices were based on a  combination of forward prices available in the market and price forecasts. 13.  INTANGIBLE ASSETS a)  Infrastructure – Utilities b)  Infrastructure – Transport The company’s Australian regulated terminal operation has access agreements with the users of the terminal which entails 100%  take or pay contracts at a designated tariff rate based on the asset value. The concession arrangement has an expiration date of  2051 and with an option to extend the arrangement an additional 50 years. The aggregate duration of the arrangement and the  extension option represents the remaining useful life of the concession. The company’s Chilean toll road concession provides the right to charge a tariff to users of the road over the term of the  concession. The concession arrangement has an expiration date of 2033, which is the basis for the company’s determination  of its remaining useful life. Also included within the company’s transport operations is $355 million (2012 – $348 million) of  indefinite life intangible assets which represent perpetual conservancy rights associated with the company’s UK port operation. The following table presents the changes to the cost of the company’s intangible assets: Valuation technique(s) Significant unobservable input(s) Relationship of unobservable input(s) to fair value Discounted cash flow models  • Future cash flows • Increases (decreases) in future cash flows will  increase (decrease) the fair value • Growth assessments • Increases (decreases) in growth assessments will  increase (decrease) the fair value • Timber/Agricultural prices • Increases  (decreases)  in  price  will  increase  (decrease) the fair value • Discount rate • Increases (decreases) in discount rate or terminal  cap rate will decrease (increase) the fair value (MILLIONS) Dec. 31, 2013 Dec. 31, 2012 Cost  $ 5,441 $ 6,115 Accumulated amortization and impairment losses  (397) (345) Total  $ 5,044 $ 5,770 (MILLIONS)  Note Dec. 31, 2013 Dec. 31, 2012 Property – Industrial, Multifamily and Other  $ 327 $ 460 Infrastructure – Utilities  (a) 2,231 2,592 Infrastructure – Transport  (b) 1,633 1,769 Private equity  257 280 Service Activities  297 371 Renewable energy  94 106 Other  205 192 Net intangible assets  $  5,044 $  5,770 Intangible assets are allocated to the following cash-generating units: YEARS ENDED DECEMBER 31  (MILLIONS) 2013 2012 Cost at beginning of year  $ 6,115 $ 4,216 Disposals, net of additions  (13) (3) Acquisitions through business combinations  20 1,916 Foreign currency translation and other  (681) (14) Cost at end of year  $ 5,441 $ 6,115 2013 ANNUAL REPORT 125