Persistently high rates of credit growth relative to GDP and seemingly high property prices could filter into lower credit ratings for banks as Standard & Poor's revises its approach to credit analysis.Amid numerous recent reviews of methods applied by the ratings agencies, in light of the credit shock, one S&P review is producing results that will demand attention by investors in bank debt and other securities.On Friday, S&P published a series of papers on its revised criteria for rating banks, and on which it seeks comment by early March.While S&P noted, in its media release, that the proposals "would have a modest impact" on banks, changes in ratings of one notch or more (and both up and down) are in prospect. In the case of Australian banks the risk of a ratings change appears to be a downside one.One of the papers summarises S&P's latest work on its "Banking Industry Country Risk Assessment" or BICRA score. These scores range from one, the safest, to 10, the riskiest.At present, S&P includes Australia's banking industry as one of six banking markets scored as a "one".Under the new approach, the S&P BICRA score for Australia's banking industry is, tentatively, a "two".The banking industry in New Zealand falls from a BICRA score of two to a score of three.S&P cites Australia's current account deficit of more than five per cent of GDP; "moderately high house price appreciation", and reliance on offshore wholesale borrowings in the order of 20 per cent to 25 per cent as factors in the lowered BICRA score for Australia.How this might translate into revised credit ratings for banks is not clear.On Friday, S&P wrote that 85 per cent of the long-term issuer credit ratings for 138 banks sampled using the new approach would remain the same or move one notch up or down. Of the remaining 15 per cent of long-term credit ratings, S&P said it found that about half moved up by more than one notch, mostly affecting niche banks, while about half moved down by more than one notch.