A big question to emerge from the release of the 2011/12 financial results of three of the Big Four banks over the past two weeks is whether the higher bad debt charges they reported signal a return to the bad debt experience of the financial crisis.The loan impairment charges of the Big Four banks increased by an average of 18.5 per cent, to A$6.2 billion, during the 2011/12 financial year. This was the first annual increase since 2008/09.National Australia Bank was the main contributor to this change, adding almost $1 billion to its bad debt charge - a 56 per cent increase. The bank attributed much of this increase to deteriorating business conditions in the United Kingdom.Westpac's charge went up 22 per cent. Commonwealth Bank's charge went down 15.9 per cent.ANZ's charge was three per cent lower than the previous year. The bank made a big cut in its collective provision, which offset an increased charge on individual exposures in its international and institutional division.A bank's collective provision is made up of a risk calculation and an overlay, which reflects the bank's view on economic and other factors. In a commentary on the results, PwC said that, leaving NAB's UK problems to one side, the increase in bad debt expense was largely the result of banks' increasing "economic overlays" in response to recent economic stress.PwC said delinquency statistics for mortgages, business loans and credit cards improved modestly. "We're not sure this trend has much further to run, given business conditions and the fact that the newest cohorts of home loans have a higher proportion of loan-to-valuation ratios at over 90 per cent," PwC said.Ernst & Young's commentary on the results also pointed to some weakening in asset quality. It said real estate markets remained "soft", with no clear sign of a recovery."Banks are closely monitoring commercial property projects, specifically large scale projects. Demand has dropped, planned returns are at risk and pre-sales are falling behind budget," Ernst & Young said.It said a number of industries, including retail, resources, manufacturing and construction, were under watch for further deterioration.However, while it warned about conditions in some parts of the economy, Ernst & Young's overall conclusion was that "current asset quality indicators are not highlighting immediate concerns of a significant deterioration."KPMG said delinquencies (90 days or more past due) fell 9.6 per cent in 2011/12. If the UK figures are excluded, even NAB's delinquencies improved."These trends suggest that the challenging macro-economic factors impacting consumer and investor confidence and ultimately business performance are not translating, in any material way, into an increase in delinquencies," KPMG said.