Surprisingly slow measure

Hi mike_asplin ,

Thanks for sharing the PBIX file.

Please try the following version of the measure. It keeps the same calculation logic as your original approach but removes the use of SUMMARIZE and ADDCOLUMNS, which are contributing to the performance issue:

AVERAGEX (
    VALUES ( DateTable[MonthYear] ),
    SUMX (
        VALUES ( Client[Client ID] ),
        CALCULATE (
            MAX ( Client[FTE Prev 30 days] )
                * [Distinct Paying Clients ex Canc]
        )
    )
)

This also avoids the “single value cannot be determined” error by explicitly resolving the client level FTE value.

Attached pbix file for reference.

Hope this helps.
Please reach out for further assistance.
Thank you.