changes in the fair value of funded and unfunded credit products are classified in principal transactions in citi 2019s consolidated statement of income . related interest revenue is measured based on the contractual interest rates and reported as interest revenue on trading account assets or loan interest depending on the balance sheet classifications of the credit products . the changes in fair value for the years ended december 31 , 2018 and 2017 due to instrument-specific credit risk totaled to a loss of $ 27 million and a gain of $ 10 million , respectively . certain investments in unallocated precious metals citigroup invests in unallocated precious metals accounts ( gold , silver , platinum and palladium ) as part of its commodity and foreign currency trading activities or to economically hedge certain exposures from issuing structured liabilities . under asc 815 , the investment is bifurcated into a debt host contract and a commodity forward derivative instrument . citigroup elects the fair value option for the debt host contract , and reports the debt host contract within trading account assets on the company 2019s consolidated balance sheet . the total carrying amount of debt host contracts across unallocated precious metals accounts was approximately $ 0.4 billion and $ 0.9 billion at december 31 , 2018 and 2017 , respectively . the amounts are expected to fluctuate based on trading activity in future periods . as part of its commodity and foreign currency trading activities , citi trades unallocated precious metals investments and executes forward purchase and forward sale derivative contracts with trading counterparties . when citi sells an unallocated precious metals investment , citi 2019s receivable from its depository bank is repaid and citi derecognizes its investment in the unallocated precious metal . the forward purchase or sale contract with the trading counterparty indexed to unallocated precious metals is accounted for as a derivative , at fair value through earnings . as of december 31 , 2018 , there were approximately $ 13.7 billion and $ 10.3 billion in notional amounts of such forward purchase and forward sale derivative contracts outstanding , respectively . certain investments in private equity and real estate ventures and certain equity method and other investments citigroup invests in private equity and real estate ventures for the purpose of earning investment returns and for capital appreciation . the company has elected the fair value option for certain of these ventures , because such investments are considered similar to many private equity or hedge fund activities in citi 2019s investment companies , which are reported at fair value . the fair value option brings consistency in the accounting and evaluation of these investments . all investments ( debt and equity ) in such private equity and real estate entities are accounted for at fair value . these investments are classified as investments on citigroup 2019s consolidated balance sheet . changes in the fair values of these investments are classified in other revenue in the company 2019s consolidated statement of income . citigroup also elected the fair value option for certain non-marketable equity securities whose risk is managed with derivative instruments that are accounted for at fair value through earnings . these securities are classified as trading account assets on citigroup 2019s consolidated balance sheet . changes in the fair value of these securities and the related derivative instruments are recorded in principal transactions . effective january 1 , 2018 under asu 2016-01 and asu 2018-03 , a fair value option election is no longer required to measure these non-marketable equity securities through earnings . see note 1 to the consolidated financial statements for additional details . certain mortgage loans held-for-sale citigroup has elected the fair value option for certain purchased and originated prime fixed-rate and conforming adjustable-rate first mortgage loans hfs . these loans are intended for sale or securitization and are hedged with derivative instruments . the company has elected the fair value option to mitigate accounting mismatches in cases where hedge accounting is complex and to achieve operational simplifications . the following table provides information about certain mortgage loans hfs carried at fair value: .
what was the percent of the carrying amount reported on the consolidated balance sheet of certain mortgage loans hfs from 2017 to 2018
the changes in the fair values of these mortgage loans are reported in other revenue in the company 2019s consolidated statement of income . there was no net change in fair value during the years ended december 31 , 2018 and 2017 due to instrument-specific credit risk . related interest income continues to be measured based on the contractual interest rates and reported as interest revenue in the consolidated statement of income. .