Summarizing Year To Date
The screenshot below shows a portion of a sub summary report that shows results of customer satisfaction surveys by month. Because the number of surveys received varies so widely from month to month, the report doesn't depict trends properly.
Instead of reporting results for each month, it should report aggregate numbers for the current month AND all preceding months. e.g. June 2013 should include June and May 2013. July 2013 should include July, June and May. etc.
I'm totally lost about how to generate a report that totals YTD results. Any suggestions would be very, very welcome.