The Best Metric That No One Uses
What is Action Rate?
For your specific attribution window, simply take the number of conversions and divide by impressions (instead of the more common clicks). This is actually the balanced product of CTR and Conversion Rate and the core component to Facebook's eCPM calculation.
Action Rate = Conversions/Impressions
Conversions/Impressions will produce a decimal with many zeroes before an interesting number. For easier data analysis and comparison, we recommend multiplying by 1,000. Multiplying by a thousand produces a metric called APM.
APM = Conversions/(Impressions/1000)
Why is Action Rate Great?
Action Rate, or its more useful cousin APM, has numerous benefits
- It is the product of CTR and Conversion rate, which allows for a cleaner view of an ad's overall effectiveness
- If you leverage view-based conversions in your model, action rate properly incorporates the combination of view and click conversions
- Conversions/Clicks can become unnecessarily elevated when views are considered. In some cases, it can equate to conversion rates >100%
- It correlates remarkably well with delivery metrics of impressions and media spend since it is the actual metric Facebook's algorithm is leveraging
How this Applies to the Bottom Line
As marketers who focus on CPA, the standard goal is to decrease this metric. There are two paths to decreasing CPA, decreasing CPM or increasing APM.
What this means is that only 3 metrics are needed to track: APM, CPM, and CPA for a business not concerned with ROAS.
If you do the math you quickly find where this insight is drawn from as
CPA = CPM/APM
This also shows the less intuitive insight that CPM can increase and CPA can decrease if the relative rate of increase in APM is higher than that of CPM. E.g. if APM increases by 10% and CPMs by 5% then CPAs will decrease by 4.56%.
How APM Plays a Role in ROAS
Our focus above was how action rate relates to CPA; however, we want to go a step forward and show how APM makes an appearance with ROAS as well.
Return On Advertising Spend, ROAS, is typically derived as follows
ROAS = Conversion Value/Amount Spent
We leave this exercise for the reader but given established definitions of AOV and CPM, ROAS can also be written as the following
ROAS = (APM*AOV)/CPM
This one looks much more complicated than the formula above. However, as a marketer, you already know what this means.
If you want to increase ROAS
- Increase the frequency someone purchases when seeing an impression: APM
- Increase the amount they buy when they purchase: AOV
- Decrease the cost to show the ad: CPM
- Increase the delta between the numerator and the denominator
If you assume that the CTR of an ad is 2% and the Conversion Rate is 2%, you will compute an Action Rate of 0.0004. Multiplying by 1000 yields an APM of 0.4.
If we assume a CPM at $10 and an AOV of $45 then the ROAS is 1.8.
So What?
Advertising is an intersection of art and science. Just look at this newsletter that begins with a creative review and ends with algebra!
The reason we enjoy discussing APM is that it is the foundation to the algebra of advertising but is ultimately a metric that measures the art of advertising. A higher APM means all the mechanisms involved (audience, creative, consumer flow, etc) are working in concert to more effectively drive conversions.
Furthermore, APM is how advertisers can understand where they should be optimizing their media and time. Should we be driving down our CPMs or looking to increase AOV? CPMs are difficult to directly influence without losing conversion efficiency, and AOV represents a lot of work around website flow, product-market fit, and general cohorts associated with your brand. APM is the metric that will illuminate which of these areas has the most opportunity.
Regardless of whether your company optimizes on a CPA or ROAS goal, APM sits at the center of those metrics.
Adding it to your set of metrics for analysis can provide crucial details in why the algorithm behaves like it does or what steps you can take to drive impact on your KPIs.
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Thanks to Rohan Makhecha for sharing their work on Unsplash.