In December, three of the Big Four banks showed some improvement in the levels of retail customer satisfaction and are close to their historically high levels.  This was according to the Roy Morgan Consumer Banking Satisfaction survey results for December 2015. The negative effect of the high-profile home-loan rate rise of the Big Four in October appears to be wearing off, at least in terms of its impact on customer satisfaction. The satisfaction levels of the Big Fours' home-loan customers improved by 0.6 per cent points in December to 78.8 per cent overall.  "We have noticed in the past that while home-loan customers are very sensitive to any rate increase, particularly when it is accompanied by high profile adverse publicity, they generally recover after a few months," said Norman Morris, industry communications director for Roy Morgan Research. The mutual banks, however, continue to set the pace in customer satisfaction with 92.1 per cent, compared to the Big Four with 80.9 per cent. The best performer among this group remans Teachers Mutual with 95 per cent satisfaction (up from 93.6 per cent 12 months ago).  "With bank customer satisfaction at historically high levels and the Big Four being closer than they've been over most of the last ten years, it is proving difficult to increase customer penetration (that is, share of wallet)," Morris said. The NAB had the biggest gain in customer penetration of the Australian 14-plus ages between December 2011 (15.0 per cent) and December 2015 (16.1 per cent).  The largest part of this gain was due to the bank's 2011 "break up" campaign, which prompted major customer growth up to 2013, according to Roy Morgan's commentary.  "Considering that the main reason for aiming for high customer satisfaction and advocacy is to attract as well as retain customers, customer penetration should be considered as a major KPI for banks." Despite the increase in home-loan customer satisfaction for the Big Four banks overall in December, they all enjoy higher satisfaction among their non-home loan customers.