How about something like the attached? Given the columns you outlined, the % Lapsed calculation is set up as:
SUM([Number Lapsed])/(SUM([Number Active])+SUM([Number Lapsed]))
The Number Payments field is set up as a discrete dimension on the Rows Shelf in order to generate a row for each value of Number Payments.
Percent Lapsed calc.twbx.zip 9.1 KB
Thanks for your suggestion Jonathan. It didn't work in this case as I need the total at 0 payments to be a constant. I sought external help and solved the problem by using the Window_max function:
sum(number_active) / window_max (sum(total gifts)) where total gifts is [Number Active]+[Number Cancelled].