Sales Percentage Change based on Fixed Year

Hi Experts

See sample PBIX FIle with data.

I am trying to work out the Percentage Change in Sales month on month based on 2019 Sales. 

so 2020 percentage change would be for JAN 20 = (jan 2020 - Jan 2019)/ Jan 2019 Sales

and

2021 Percentage change (based on 2019 sales) for JAN 21 = (jan 2021 - Jan 2019)/ Jan 2019 Sales

My Measure =

Divide(Calculate(Average(SampleData[Average of IEA Demand]),ALL(DimDate[Date])),[Demand Perious Yr], blan())

Where Demand Previous Yr = Calculate(Average(SampleData[Average of IEA Demand]), Sameperiodlastyear(DimDate[Date])

As you can see from the sample data the (column) % Change MoM Movement - is correct for so 2020 percentage change would be for JAN 20 = (jan 2020 - Jan 2019)/ Jan 2019 Sales, but Wrong for the following year i.e.

2021 percentage change would be for JAN 21 = (jan 2021 - Jan 2019)/ Jan 2019 Sales.

https://www.dropbox.com/s/o7i3v62rw70lx6s/Sample_.pbix?dl=0