Returning results including rows with 0 incidents for the month

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I have a report which is summing up incidents based on items in a custom drop down field. I can't show you the actual results because of confidential data.  But essentially, the issue types in the drop down are how I am summing up the count of incidents for the month.

There are about 60 items in the drop down list on the form that is used to submit these incidents.  In any given month, I don't expect to have all of these items used.  But for consistency across months when these are exported to Excel and combined with previous months in various ways, I would like to return a row for each of the 60 items whether there was an incident for that item that month or not.