Average calculation

Anonymous 

I rewrote it to use a couple measures.

1. Just the count of records.

Matter Key Count = COUNT( 'WL Matter Extract'[MATTER_KEY] )

2. A YTD running total of that count

Cummulative Count = 
CALCULATE ( [Matter Key Count], DATESYTD ( 'Calendar Date'[Date] ) )

3. A YTD active months count.  Only count months that have records in the 'WL Matter Extract' table

Cummulative Month Count = 
CALCULATE (
    COUNTROWS (
        CALCULATETABLE (
            VALUES ( 'Calendar Date'[Month Year] ),
            'WL Matter Extract'
        )
    ),
    DATESYTD ( 'Calendar Date'[Date] )
)

The Avg measure, where I only show the amount on months that have records to keep it from rolling forward to all future moths in the year.

Avg = 
VAR _Count = [Matter Key Count]
VAR _YTDCount = [Cummulative Count]
VAR _Months = [Cummulative Month Count]
RETURN DIVIDE ( _Count, _Count ) * DIVIDE ( _YTDCount, _Months )

I have attached my sample file for you to look at.