YOY Calculation

-- Assumptions:
-- T is the table
-- RatingYear is integer

-- Questions:
-- What's the use of PlanID if in the
-- sample data set it's all the same?

-- calculated column
[PreviousYearRating] =
var __currentYear = T[RatingYear]
var __prevYear = __currentYear - 1
var __currentCompetitor = T[Competitors]
-- If this calculation is slow, then one has
-- to use an alternative that will not use
-- CALCULATE but only FILTER on its own.
var __prevYearRating =

     CALCULATE(
        VALUES( T[Rating] ),
        T[Competitors] = __currentCompetitor,
        T[RatingYear] = __prevYear,
        ALL ( T )
    )
return
	__prevYearRating
	
-- calculated column
-- Please do not multiply the output by 100.
-- Use formatting to format the number correctly as percentage.
[YOY%] =
var __currentRating = T[Rating]
var __prevYearRating = T[PreviousYearRating]
var __yoy = DIVIDE( __currentRating, __prevYearRating )
return
	__yoy

Best

Darek