Fair Value Hierarchy Levels  2013 ANNUAL REPORT 111 Fair values determined using valuation models (level 3 financial assets and liabilities) require the use of assumptions concerning  the amount and timing of estimated future cash flows and discount rates. In determining those assumptions, the company looks  primarily to readily observable external market inputs such as interest rate yield curves, currency rates, and price and rate  volatilities, as applicable.  There were no transfers between level 1 and level 2 in 2013 or 2012.  Fair values for financial instruments are determined by reference to quoted bid or ask prices, as appropriate. Where bid and ask  prices are unavailable, the closing price of the most recent transaction of that instrument is used. In the absence of an active  market, fair values are determined based on prevailing market rates for instruments with similar characteristics and risk profiles  or internal or external valuation models, such as option pricing models and discounted cash flow analysis, using observable  market inputs. Level 2 financial assets and financial liabilities include foreign currency forward contracts, interest rate swap agreements, energy  derivatives, interests of others in consolidated funds and equity derivatives. The following table summarizes the valuation techniques and key inputs used in the fair value measurement of level 2 financial  instruments: Type of asset/liability Valuation technique(s) and key input(s) Foreign currency forward  contracts  Discounted cash flow model – forward exchange rates (from observable forward exchange rates at  the end of the reporting period) and discounted at credit adjusted rate Interest rate contracts  Discounted cash flow model – forward interest rates (from observable yield curves) and applicable  credit spreads discounted at a credit adjusted rate  Energy derivatives  Quoted market prices, or in their absence internal valuation models corroborated with observable  market data Interest of others in  consolidated funds  Adjusted public pricing Dec. 31, 2013 Dec. 31, 2012 (MILLIONS) Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Financial assets Other financial assets Government bonds  $  41 $  138 $  — $  52 $  126 $  — Corporate bonds  20 299 — 59 179 — Fixed income securities  44 55 113 88 — 57 Common shares and warrants  838 1 1,919 423 — 1,611 Loans and notes receivables  — 23 8 — 25 10 Accounts receivable and other  131 343 689 — 112 656 $ 1,074 $ 859 $ 2,729 $ 622 $ 442 $ 2,334 Financial liabilities Accounts payable and other  $ 117 $ 1,046 $ 142 $ 262 $ 697 $ 328 Interests of others in consolidated funds  — 139 947 — 73 352 $ 117 $ 1,185 $ 1,089 $ 262 $ 770 $ 680 Assets and liabilities measured at fair value on a recurring basis include $2,729 million (2012 – $2,334 million) of financial  assets and $1,089 million (2012 – $680 million) of financial liabilities which are measured at fair value using unobservable  valuation inputs or based on management’s best estimates. The following table categorizes financial assets and liabilities, which  are carried at fair value, based upon the fair value hierarchy levels: