The secular shift in the drivers of demand for payments cards continues to be feature of the monthly flow of data on this product segment from the Reserve Bank of Australia. One highlight in the data for May, released yesterday, is the decline in the value of purchases made with a personal credit card to less than 50 per cent of all purchases.Purchases made with personal credit cards have dropped from 54.3 per cent of the value of all purchases made with payments cards in the year to May 2008 to 49.5 per cent in the year to May 2011.This shift may be accelerating, with the growth in purchases on all credit card accounts rising by only two per cent over the last year, while purchases on charge and commercial cards increased by 10 per cent, according to the monthly analysis on payment card trends compiled by MWE Consulting.This trend is one variation in the underlying shift to purchases being made using debit cards. "A switch in cardholder preference to debit [that] shows no sign of abating," according to Mike Ebstein, principal of MWE.One illustration of this trend, shown in today's chart, is the 12-month growth in spending on credit cards and debit cards over recent years, with the debit data covering spending both on Eftpos and scheme debit cards.Annual growth spending on credit cards, at four per cent, is flagging once more, after a brief recovery in mid-2010 following the period of post-GFC conservatism.Growth in spending on debit cards, at 18 per cent over one year, is also easing and is consistent with other economic indicators showing sluggish retail sales, as well as subdued consumer and business confidence.At least one bank is now releasing overviews of card spending data on a more timely basis - based on card-holder use and merchant sales.A couple of months ago, ANZ's economics team began producing a "monthly sales index", along the lines of the retail sales index formerly produced by Cashcard.