The relationship between marketing investment and return typically exhibits diminishing returns to scale properties.
This means, the more you spend, the less return you achieve as the channel becomes more saturated. Adtriba calculates this relationship as part of the modeling process and displays it to the user in the saturation curve panel.
On the other hand, we provide a fitting metric in the performance table to you: the marginal CPA.
This KPI reflects the saturation of your source. The more saturated a source is, the higher will be the marginal CPA. Hence you should watch out for the sources with a rather low marginal CPA in comparison to either scale your budget up or shift it accordingly.