The Big Four banks are closing the gap with their smaller rivals in the customer satisfaction stakes.DBM Consultants reported in its latest Business Financial Services Monitor, released this week, that the average rating of the Big Four was 1.4 points (on a scale of 10) behind the average rating of the regional banks at the start of the year. In the latest survey the gap has narrowed to 0.9 points.DBM measures the responses of business customers. A similar trend has been observed in recent Roy Morgan retail customer surveys.DBM managing director Dhruba Gupta said: "The major banks have made a very concerted effort."Gupta said Commonwealth Bank was the big improver in 2011, while Westpac has consistently had the highest overall ratings among the Big Four.DBM divides its business customer respondents into four groups - large, medium, small and micro. Gupta said the Big Four still had work to do in the small business segment (turnover of A$1 million to $5 million), where the regionals had significantly higher satisfaction scores.Westpac achieved the best Big Four rating, with an average score of 7.5 (out of 10) across all business segments. Commonwealth Bank had a score of 7.3, ANZ had 7.1 and National Australia Bank had 6.9.