Expressions between dates grouped by years

[#1]

I have a question about set analisys and date ranges. I use Qlikview 9 sr 4.

I have this set analisys expression:

=sum

(

    {$<DocumentDate = {'>=$(=Date(MinDate))<=$(=Date(MaxDate))'}>}

     (DataValues_MS)

)

/

=sum

(

    {$<DocumentDate = {'>=$(=Date(MinDate))<=$(=Date(MaxDate))'}>}

     (DataValues_NT)

)

I have a pivot table in wich if I select for example year 2012, the result is 14,011, then if I select year 2013 the result is 10,502 and all result for the single year selection are correct.

But when I select 2012 and 2013, in my pivot table for each year I have the same result, 12,591

How I can I obtain the correct values when 2012 and 2013 years are both selected?

Can anyone help me in the solution of this case?

Thanks.