Create a straight table with dimension
=Aggr(if(sum(TOTAL <Year> Amount) > Avg(TOTAL Aggr(sum(Amount),Year)),'Above Avg', 'Below Avg'),Year)
and with this expression
Concat(DISTINCT Year,', ')
And you get this.
Compare with Avg Year Above Avg 2012 Below Avg 2013
Add more years' data and the expression will list all the years separated by a ','.
add a further expression count(DISTINCT Year) and you get
Compare with Avg Year Count of Year Above Avg 2012 1 Below Avg 2013 1