Could you post a packaged workbook showing the work you've tried?
Sounds like possibly do it with LODs. FIX one LOD on the year of 2016 and one on the region with a clause of year = 2016. Then do the same with 2015. End up with 4 LODs but those should be divisible at the level you have in your viz. Could be slow but would work. As Diego says a workbook of sanitized data helps, along with the result you're expecting.