Calculating Average question

You can straight use AVERAGEX to iterate through the value of each year before getting the average

Units Sold Yearly Avg =

AVERAGEX (                         -- Calculate the average across the years

    VALUES ( 'Date'[Year] ),       -- Get each selected year

    [Units Sold]                   -- Calculate Units Sold for each year

)

Note:  AVERAGEX  exclude blank rows. In the example below, although there are 16 years from 1999 to 2014, 1999 is blank so the average is 118500/15 = 7900