Valuations utilize significant unobservable inputs (level 3) when determining the fair value of property assets. The significant  level 3 inputs include: Key valuation assumptions included a weighted average discount rate of 10.5% (2012 – 9.9%), terminal capitalization rate of  7.6% (2012 – 7.5%), and investment horizon of 7 years (2012 – 5 years). The following table presents the changes to the cost of the company’s property, plant and equipment assets included within its  property operations: The following table presents the changes to the accumulated fair value changes of the company’s property, plant and equipment  within its property operations: The following table presents the changes to the accumulated depreciation of the company’s property, plant and equipment within  its property operations: Other property, plant and equipment includes asset owned by the company’s private equity, residential development and service  operations held directly or consolidated through funds. 2013 ANNUAL REPORT 123 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 pricing, volumes  and direct operating costs • 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  decrease (increase) the fair value YEARS ENDED DECEMBER 31  (MILLIONS) 2013 2012 Balance at beginning of year  $  3,130 $  640 Additions, net of disposals  137 44 Acquisitions through business combinations  — 2,446 Foreign currency translation  (99) — Balance at end of year  $ 3,168 $ 3,130 YEARS ENDED DECEMBER 31  (MILLIONS) 2013 2012 Balance at beginning of year  $ 4 $ — Fair value changes  166 4 Foreign currency translation  — — Balance at end of year  $ 170 $ 4 d)  Private Equity and Other YEARS ENDED DECEMBER 31  (MILLIONS) 2013 2012 Balance at beginning of year  $ (166) $ — Depreciation expense  (130) (166) Balance at end of year  $ (296) $ (166) (MILLIONS) Dec. 31, 2013 Dec. 31, 2012 Cost  $ 3,984 $ 3,887 Accumulated fair value changes  (256) (162) Accumulated depreciation  (926) (813) Total  $ 2,802 $ 2,912