credit commitments and lines of credit the table below summarizes citigroup 2019s credit commitments : in millions of dollars u.s .outside of u.s .december 31 , december 31 .
[['in millions of dollars', 'u.s .', 'outside ofu.s .', 'december 312018', 'december 31 2017'], ['commercial and similar letters of credit', '$ 823', '$ 4638', '$ 5461', '$ 5000'], ['one- to four-family residential mortgages', '1056', '1615', '2671', '2674'], ['revolving open-end loans secured by one- to four-family residential properties', '10019', '1355', '11374', '12323'], ['commercial real estate construction and land development', '9565', '1728', '11293', '11151'], ['credit card lines', '605857', '90150', '696007', '678300'], ['commercial and other consumer loan commitments', '185849', '102918', '288767', '272655'], ['other commitments and contingencies', '2560', '761', '3321', '3071'], ['total', '$ 815729', '$ 203165', '$ 1018894', '$ 985174']]
the majority of unused commitments are contingent upon customers maintaining specific credit standards .commercial commitments generally have floating interest rates and fixed expiration dates and may require payment of fees .such fees ( net of certain direct costs ) are deferred and , upon exercise of the commitment , amortized over the life of the loan or , if exercise is deemed remote , amortized over the commitment period .commercial and similar letters of credit a commercial letter of credit is an instrument by which citigroup substitutes its credit for that of a customer to enable the customer to finance the purchase of goods or to incur other commitments .citigroup issues a letter on behalf of its client to a supplier and agrees to pay the supplier upon presentation of documentary evidence that the supplier has performed in accordance with the terms of the letter of credit .when a letter of credit is drawn , the customer is then required to reimburse citigroup .one- to four-family residential mortgages a one- to four-family residential mortgage commitment is a written confirmation from citigroup to a seller of a property that the bank will advance the specified sums enabling the buyer to complete the purchase .revolving open-end loans secured by one- to four-family residential properties revolving open-end loans secured by one- to four-family residential properties are essentially home equity lines of credit .a home equity line of credit is a loan secured by a primary residence or second home to the extent of the excess of fair market value over the debt outstanding for the first mortgage .commercial real estate , construction and land development commercial real estate , construction and land development include unused portions of commitments to extend credit for the purpose of financing commercial and multifamily residential properties as well as land development projects .both secured-by-real-estate and unsecured commitments are included in this line , as well as undistributed loan proceeds , where there is an obligation to advance for construction progress payments .however , this line only includes those extensions of credit that , once funded , will be classified as total loans , net on the consolidated balance sheet .credit card lines citigroup provides credit to customers by issuing credit cards .the credit card lines are cancelable by providing notice to the cardholder or without such notice as permitted by local law .commercial and other consumer loan commitments commercial and other consumer loan commitments include overdraft and liquidity facilities as well as commercial commitments to make or purchase loans , purchase third-party receivables , provide note issuance or revolving underwriting facilities and invest in the form of equity .other commitments and contingencies other commitments and contingencies include committed or unsettled regular-way reverse repurchase agreements and all other transactions related to commitments and contingencies not reported on the lines above .unsettled reverse repurchase and securities lending agreements and unsettled repurchase and securities borrowing agreements in addition , in the normal course of business , citigroup enters into reverse repurchase and securities borrowing agreements , as well as repurchase and securities lending agreements , which settle at a future date .at december 31 , 2018 , and 2017 , citigroup had $ 36.1 billion and $ 35.0 billion unsettled reverse repurchase and securities borrowing agreements , respectively , and $ 30.7 billion and $ 19.1 billion unsettled repurchase and securities lending agreements , respectively .for a further discussion of securities purchased under agreements to resell and securities borrowed , and securities sold under agreements to repurchase and securities loaned , including the company 2019s policy for offsetting repurchase and reverse repurchase agreements , see note 11 to the consolidated financial statements. .

Question: what percentage of total credit commitments as of december 31 , 2018 are credit card lines?
Answer: 68%