In order to determine how many parishioners unregistered in the past year, you'll need to build an IQ Query.
1. Insert all the Result Columns that you'll want to know about these parishioners. Include: Family > Date Unregistered
2. In the Query Conditions add: Family > Date Unregistered. Set "is equal to," to "custom period" and then insert the date range you'd like:
3. Select "Execute Query"
4. Export the results to Excel by clicking "Query Results" > "Export to CSV" and then see how many rows there are to get the number of families.