How to build a report showing a distribution

Any idea how I can show a report showing a distribution of values? I am tracking Client retention days..and I would like to show a distribution of Clients by their days retention....so I can see if we are improving our overall retention of clients. I can show a bar graph now showing retention days by month...and can get some info by clicking on each bar to get a listing of clients in that grouping...but it would be easier to show the days retained on the ordinate and the # clients on the abscisa ...any clue???