China UnionPay has become "the most popular payment method based on purchase volume", US researcher The Nilson Report said in its annual report, Global Cards.Purchases for goods and services from merchants worldwide in 2013 grew by US$2.8 trillion or 22 per cent to US$15.4 trillion.The trend may give impetus to discussions among banks in Australia about issuing CUP cards.China UnionPay might be close to issuing credit cards and scheme debit cards in the Australian market, if soundings by competitors are on the money.Visa International, in its submission to the Financial System Inquiry, asserts that "we understand that China UnionPay has well developed plans to launch a four party model card in Australia."Other evidence for this is thin, though banks are jockeying to accommodate the Chinese card scheme, at least on the acceptance side.Westpac yesterday said it had reached agreement to accept China UnionPay cards in Australia via ATMs, merchant terminals and online payment facilities. It is the last major bank to do so, although ANZ is yet to implement acceptance for CUP in Australia.Comparing debit card purchase volume only, UnionPay's global share increased 738 basis points to 47.2 per cent, The Nilson Report said in analysis released yesterday."This gain made UnionPay the largest general purpose debit card issuer based on purchase volume," it said.The Nilson Report said these "for the first time surpassed Visa credit cards and Visa debit cards."Visa's share fell 605 bps to 40.6 per cent while MasterCard's share declined by 133 bps to 12.2 per cent. Comparing credit card purchase volume only, Visa's market share was39.2 per cent in 2013, down 262 bps. MasterCard's share dropped 158 bps to 26.1 per cent. UnionPay's share grew by 534 bps to 20.4 per cent. American Express's share fell 109 bps to 11.8 per cent.