Cumulative Cohort analysis

From the learning summit Series ‘Cohort Analysis Introduction’ how do we make the ‘Retention %’ Cumulative %?

Retention % = 
CALCULATE(
    DIVIDE( [Retention Period], [Unique Customers], 0 ),
        TREATAS( VALUES( Dates[Month & Year] ), Customers[Join Month Cohort] ) )

Welcome to the Enterprise DNA Forum @Mwoody_05. We’re happy to have you in the community. To get started, I highly suggest you check these guides that Sam created for us to build a more collaborative environment. How To Use The Enterprise DNA Support Forum