Deferred ratio by Sprint

I have tried with no success to create a report on deferred items. Does anyone know if there is a plan to include this report into the Scrum process or anyone has developed such.
The current deferred report is chart within sprint but what I would like to have is a report that charts the deferred items by sprint to understand how many items (or story points) the team is deferring on each iteration.
Basically, it would be:
Deferred Ratio = (#Deferred work items / # Total work items )
plotted by sprint.

Thanks.