National Australia Bank has achieved a big improvement in its business banking customer satisfaction ratings over the past 12 months. The latest DBM consultants Business Financial Services Monitor shows that NAB has moved from the back of the pack a year go to equal footing with the leaders.NAB's whole-of-market satisfaction rating rose from 7.1 (out of ten) in June last year to 7.3 in December.Commonwealth Bank has a rating of 7.4 and Westpac 7.3. ANZ is trailing the field with a rating of 7.1.DBM Consultants director Maria Claridad said NAB's improvement was the result of greater commitment to its business customers across all market segments.Claridad said in a statement: "It is difficult to do things consistently well across the board and we often find that when there is an increase in one segment there could be a decline in another."NAB's satisfaction scores have improved in all segments over the past year - micro, small medium and large business. However, its best result is in the medium business segment (annual sales of A$5 million to $50 million), where it is the clear leader with a rating of 7.6.Among the other big banks, CBA and Westpac lost a little ground over the past year, while ANZ has bounced along the bottom without any change to its rating.