Help Calculating Last Year Value and % Change for a Measure

[Anonymous]

I have a calculated measure, $ per item (SUM(billed dollars)/SUM(item volume). What I am trying to do eventually is calculate the % change compared to a prior year. From my understanding I first need a value for Last Year $ per item before I can calculate this. So for example I am looking at something like this: 

YEAR     January

2018      $40.79

2019      $43.89

In the end I am looking for the % change compared to prior year: approx. 7%

I have tried the following already: 

$per item LY = CALCULATE([$ per item],SAMEPERIODLASTYEAR([EnteredDate])) <-returns all blanks

$ per item % Change =

IF(

    ISFILTERED('vw_xxx'[EnteredDate]),

    VAR __PREV_YEAR =

        CALCULATE(

            [$ per item],

            DATEADD('vw_xxx'[EnteredDate], -1, YEAR)

        )

    RETURN

        DIVIDE([$ per Item] - __PREV_YEAR, __PREV_YEAR)

)

 Which also returns all blanks.

[Anonymous]

Also to clarify that example data is how I'm looking at it in a matrix, it is not my table.