National Australia Bank's break-up marketing strategy has not given it any advantage in terms of customer satisfaction. The bank's satisfaction score has gone up in recent months but so have those of the other banks.The latest Roy Morgan Research consumer banking customer satisfaction report, released yesterday, shows that all four big banks have recovered much of the ground they lost with customers late last year when some of them made out-of-cycle interest rate increases.Westpac's satisfaction ratings went up 1.1 percentage points in the three months to the end of May, ANZ's and NAB's ratings went up 60 basis points over the same period and Commonwealth's went down 20 basis points (it made an 80 basis point gain in May).NAB is ranked third among the big four, with a score of 72.8 per cent. ANZ has the top rating, at 75.7 per cent, followed by Westpac (75 per cent). Commonwealth has a rating of 72.3 per cent.According to Roy Morgan's industry communications director, Norman Morris, NAB's computer system breakdowns this year have cost it some support.