How to make a Percentage Change Column in Matrix Table

Hi derekli1700 

Make sure to use a separate dates table and mark it as a date table

Create a one-to-many single direction relationship

Create this measure

Delta = 
VAR PrevYear =
    CALCULATE ( [Count], SAMEPERIODLASTYEAR ( CalendarTable[Date] ) )
VAR Difference = [Count] - PrevYear
RETURN
    DIVIDE ( Difference, PrevYear )

Please see attached sample pbix