percentages based on date and not on grand total

I'm trying to determine what percentage of our rental accounts each year pay via auto-debit, and what percentage do not.

I've gotten close, I think.  See below:



Ignoring the pie chart and only looking at the column chart, everything is correct except the percentages.  I want to see the two percentages (where the arrow is, and likewise for each column) to add up to 100%, with the Y-axis being the total number of rentals in a given year.  The totals are all there, but because I went to the Values section and changed to "percentage of grand total," it gave me what you see here (percentages based on all rentals rather than all rentals within a given year).

Thanks for your help.