Satisfaction levels among the Big Four banks' personal customers rose from 79.5 per cent in November last year, to 79.9 per cent in December, the latest Roy Morgan data reveals.But Roy Morgan also found, based on up to 10,000 bank customer interviews, that the top-quintile had the lowest satisfaction level of all the quintiles (73 per cent) and the lowest level of advocacy, with a 'net promoter score' of minus 24, well below the Big Four's overall average of minus 8.6.This is cause for concern, according to Roy Morgan, as the top ranked group accounts for 63 per cent of the total value of the financial services market across all banking and wealth-management products. Conversely, the highest satisfaction levels for each of the Big Four banks are to be found among their lowest-quintile customers (bottom 20 per cent of assets and transactions by value). But as this group accounts for only 0.3 per cent of the total market value and banks already have a high share of wallet (around 70 per cent), they have very little growth potential. At the smaller banks, satisfaction levels among their high potential value customers (top quintile) are much higher than at the Big Four. The best performer of the 12 largest banks was Teachers Mutual Bank with 96.1 per cent satisfaction, followed by Bendigo Bank (91.6 per cent) and ING Direct (87.8 per cent).Bank customers in the top quintile also have the lowest 'net promoter score' or advocacy levels. Norman Morris, industry communications director at Roy Morgan Research, said that over the last decade, advocacy (or net promoter score) has been used in addition to satisfaction as an important metric to assist banks in improving their level of customer focus. "This research shows that there is now a big opportunity to focus both satisfaction and advocacy on the more important segments rather than simply a total market measure" Morris said.He suggested that as each of the four major banks has less than a third of their top-quintile customers' wallets, this metric should become the measure of real marketing success, alongside satisfaction and NPS.