The following table presents the change in the fair value of investment properties, all of which are considered level 3 within the  fair value hierarchy: 10.  INVESTMENT PROPERTIES YEARS ENDED DECEMBER 31  (MILLIONS) 2013 2012 Fair value at beginning of year  $ 33,161 $ 28,366 Additions  1,835 1,715 Acquisitions through business combinations  5,530 2,793 Disposals  (1,908) (1,136) Fair value changes  1,031 1,276 Foreign currency translation  (1,313) 147 Fair value at end of year  $ 38,336 $ 33,161 Valuation technique(s) Significant unobservable input(s) Relationship of unobservable input(s) to fair value Discounted cash flow models • Future cash flows primarily  driven by net operating income • Increases (decreases) in future cash flows will  increase (decrease) the fair value • Discount rate • Increases (decreases) in discount rate will decrease  (increase) the fair value • Terminal capitalization rate • Increases (decreases) in terminal capitalization rate  will decrease (increase) the fair value • Investment horizon • Increases (decreases) in the investment horizon will  increase (decrease) the fair value Office Retail Multifamily, Industrial and Other Weighted Average AS AT DECEMBER 31 2013 2012 2013 2012 2013 2012 2013 2012 Discount rate  7.4% 7.6% 9.2% 8.7% 8.6% 8.8% 7.7% 7.8% Terminal capitalization rate  6.3% 6.5% 7.6% 7.5% 7.5% 8.1% 6.6% 6.8% Investment horizon (years)  11 11 10 10 10 10 11 11 (MILLIONS) Dec. 31, 2013 Dec. 31, 2012 Cost  $ 23,466 $ 22,858 Accumulated fair value changes  11,599 11,398  Accumulated depreciation  (4,046) (3,108) Total  $ 31,019 $ 31,148 11.  PROPERTY, PLANT AND EQUIPMENT Investment properties include the company’s commercial, retail, multifamily and industrial properties as well as higher-and- better use land within the company’s sustainable resource operations. Significant unobservable inputs (level 3) are utilized when determining the fair value of investment properties. The significant  level 3 inputs include: Key valuation metrics of the company’s investment properties are presented in the following table on a weighted-average basis: Accumulated fair value changes include revaluations of property, plant and equipment using the revaluation method, which are  recorded in revaluation surplus, as well as unrealized impairment losses recorded in net income. 116 BROOKFIELD ASSET MANAGEMENT 