In reply to Matthew Williamson.

Maybe I should have said "internationally accepted"; regardless, Visa is apparently still the largest issuer of credit cards ...

“In terms of transaction volume, China UnionPay is already the world’s second largest card company, behind industry leader Visa. UnionPay has 31 per cent of global market share compared to Visa’s 40 per cent. Mastercard is the third most accepted card, with 24 per cent of the market.”—June 2014
http://www.businessspectator.com.au/article/2014/6/19/china/worlds-largest-payment-card-company-youve-probably-never-heard

“Based on payments volume, total volume and number of transactions, Visa is the largest retail electronic payments network in the world. The following chart compares our network with those of our major general purpose payment network competitors for calendar year 2011:”
See chart on page 14 of Visa’s Form 10-K at …
http://www.sec.gov/Archives/edgar/data/1403161/000138410812000011/v09301210-k.htm