Vanity metrics sneak into cohort reviews as cumulative installs, session counts without revenue, or ROAS calculated before refunds settle. They create energetic meetings and poor decisions.
Put payback week on the wall
For each acquisition week, track when contribution margin covers that week’s CAC. The shape of that curve matters more than any single day-zero ratio.
Cap the chart at decisions
If a number cannot change creative, bid, or budget this week, keep it off the primary slide. Secondary diagnostics belong in an appendix, not the opening frame.
Watch for partial weeks
Comparing a Monday-started cohort to a Friday-started cohort without normalization invents fake wins. Align windows or annotate incomplete weeks clearly.
Our ROI Lens page summarizes how these cohort habits fit the wider trail.