Hi, Thanks for looking into it. Here's the code: ( ParallelPeriod(_Sum_, 'Aantal spelers'n, 'Peildatum'n, _Inferred_, _ByYear_, 0, _ToToday_, {Date}) - ParallelPeriod(_Sum_, 'Aantal spelers'n, 'Peildatum'n, _Inferred_, _ByYear_, -1, _ToToday_, {Date}) ) / Abs(ParallelPeriod(_Sum_, 'Aantal spelers'n, 'Peildatum'n, _Inferred_, _ByYear_, -1, _ToToday_, {Date})) Hope you can find out what's wrong. I tried using YOY in several reports but it never works. Neither do other 'Create and add' calculations. Thanks! Nicky
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