If I have a hierarchy for Year and then Month. I expand out 2012 month 1-12 and 2013 month 1-12
I have a value (say total sales) and I right click on it and do Show Values As: Difference From -> Base Field -> Month (previous)
It works great, right up to Month 1 of 2013. That is blank and does not compare against month 12 of the last year (2012).
Is there some way around this or some adjustment to rectify this odd behavior?