End of analysisNext steps and reference material below. Not part of the analysis result.
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Budget moves
Full journey
Can I put more budget into this channel?
If marginal CPA far exceeds average CPA, it is already saturated.
Method and FAQOpen only when you need the methodology
See how the saturation index is computed and its limits
When to use it
Use it for scale-up requests, before pushing a well-performing channel further, or when a budget increase did not produce a proportional lift. Curve estimates are meaningful only when spend has been observed at several levels.
What it calculates
A response curve is fitted from observed spend and outcomes, the marginal efficiency is taken at the current spend point, and the ratio to average efficiency becomes the saturation index. Above one means the next unit performs worse than the average; lower values indicate remaining headroom.
How to act
Send scalable channels to the allocation simulator as scale-up candidates, and saturated channels toward reduction or structural change in targeting, creative, and bidding. Estimates far outside the observed spend range lose reliability quickly, so treat the tail of the curve as indicative only.
Frequently asked questions
Does a saturated verdict mean I must cut spend?
Not necessarily. It means the next unit performs worse than the average. If the channel still meets your target CPA, holding spend while changing creative or targeting is a valid response.
Can new channels with little data be judged?
With only a few observed spend levels the curve is unstable. Treat those channels as an experiment budget rather than a verdict.
Can I evaluate with ROAS instead?
Yes. For ROAS the ratio inverts (average ÷ marginal), and the table, chart, and caption units switch together.