Break-even MER vs break-even ROAS

The same idea at two levels

• Break-even ROAS applies to attributed revenue, so it belongs to one platform or one campaign.
• Break-even MER applies to total store revenue and total marketing spend, so it belongs to the month.

Both are one divided by a margin share, and they usually differ because the two revenues are not the same revenue.

When to use which

• Use break-even ROAS to decide whether an ad set should scale, hold or stop.
• Use break-even MER to decide whether marketing as a whole paid for itself.
• Do not compare platform ROAS with break-even MER, or the other way round.

Why they can disagree

Platforms overlap, so summed platform revenue can exceed the store's revenue. A campaign can clear its break-even ROAS while the month misses break-even MER, and the reverse can also happen.

Report both, labelled

Put MER and its break-even line at the top. Show platform ROAS below with the attribution window written beside it. Say plainly that platform figures overlap.