Big banks have worked hard to differentiate themselves from each other as part of their strategy to improve customer satisfaction, but the latest Roy Morgan Research report shows that their satisfaction scores have never been closer together. There are 3.7 percentage points separating the ratings of the Big Four in Roy Morgan's retail customer satisfaction survey for April, released yesterday. ANZ leads with a score of 75.2 per cent, followed by Westpac on 73.9 per cent, NAB on 72.3 per cent and Commonwealth on 71.5 per cent Throughout most of the past decade around 10 percentage points, and often more, has separated the four banks. The gap between the big banks and their smaller rivals is also closing. Back around 2000, the difference between the average ratings of the major banks and the top-rated Bendigo Bank was around 30 percentage points. Today it is 15 points. The big banks are also closing in on the building societies and credit unions, although it will be at least another decade before they get within striking distance of the kind of scores that highly rated mutuals enjoy. Teachers Credit Union has a 95 per cent satisfaction rating, Newcastle Permanent Building Society has a 90.8 per cent rating and Greater Building Society has 90.7 per cent.