largest operators of open-loop and closed-loop retail electronic payments networks the largest operators of open-loop and closed-loop retail electronic payments networks are visa , mastercard , american express , discover , jcb and diners club . with the exception of discover , which primarily operates in the united states , all of the other network operators can be considered multi- national or global providers of payments network services . based on payments volume , total volume , number of transactions and number of cards in circulation , visa is the largest retail electronic payments network in the world . the following chart compares our network with those of our major competitors for calendar year 2007 : company payments volume volume transactions cards ( billions ) ( billions ) ( billions ) ( millions ) visa inc. ( 1 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $ 2457 $ 3822 50.3 1592 .

1	company	payments volume ( billions )	total volume ( billions )	total transactions ( billions )	cards ( millions )
2	visa inc. ( 1 )	$ 2457	$ 3822	50.3	1592
3	mastercard	1697	2276	27.0	916
4	american express	637	647	5.0	86
5	discover	102	119	1.6	57
6	jcb	55	61	0.6	58
7	diners club	29	30	0.2	7

( 1 ) visa inc . figures as reported previously in our filings . source : the nilson report , issue 902 ( may 2008 ) and issue 903 ( may 2008 ) . note : visa inc . figures exclude visa europe . figures for competitors include their respective european operations . visa figures include visa , visa electron , and interlink brands . visa cards include plus proprietary cards , but proprietary plus cash volume is not included . domestic china figures are excluded . mastercard figures include pin-based debit card figures on mastercard cards , but not maestro or cirrus figures . china commercial funds transfers are excluded . american express and discover include business from third-party issuers . jcb figures are for april 2006 through march 2007 , but cards and outlets are as of september 2007 . jcb total transaction figures are estimates . our primary operations we generate revenue from the transaction processing services we offer to our customers . our customers deliver visa products and payment services to consumers and merchants based on the product platforms we define and manage . payments network management is a core part of our operations , as it ensures that our payments system provides a safe , efficient , consistent , and interoperable service to cardholders , merchants , and financial institutions worldwide . transaction processing services core processing services our core processing services involve the routing of payment information and related data to facilitate the authorization , clearing and settlement of transactions between visa issuers , which are the financial institutions that issue visa cards to cardholders , and acquirers , which are the financial institutions that offer visa network connectivity and payments acceptance services to merchants . in addition , we offer a range of value-added processing services to support our customers 2019 visa programs and to promote the growth and security of the visa payments network . authorization is the process of approving or declining a transaction before a purchase is finalized or cash is disbursed . clearing is the process of delivering final transaction data from an acquirer to an issuer for posting to the cardholder 2019s account , the calculation of certain fees and charges that apply to the issuer and acquirer involved in the transaction , and the conversion of transaction amounts to the .

Question: what was the total payment volume for american express, in billions?
Answer: 637