How to write DAX measure to calculate average for year

I've like t write a measure to calculate the average sales for each year;


I've tried a couple of methods, one ;

 CALCULATE([Tunits], ALL('Calendar'),VALUES('Calendar'[Year]) ) / 12

Which give the correct answer providing all dates / months have values in them
I have also used AVERAGEX with crossjoin,

 AVERAGEX(CROSSJOIN(ALL('Calendar'[Month]),VALUES('Calendar'[Year])),[Tunits])

This works but can I just use average and wrap in calculate to remove or keep filter context as required, as for the denominator in a percentage?

Workbook attached.

Richard.