Understanding The Email 'Frequency Math Effect'

Finding the right email frequency is one of the many issues that email marketers have to figure out in order to have a successful email program. What happens when they change their email cadence, such as emailing on more days of the week or emailing more than once a day at different times of the year?

That was one of the questions my company wanted to answer in its annual study of email marketing benchmarks. We found some interesting results when we compared email activity on retail and ecommerce messages sent between Black Friday and New Year's Eve:

-- Open and click-through rates were lower in this period compared with emails sent the rest of the year. The mean (average) unique open rate during the holiday period was 17.6%,  compared with 20.9% for the rest of the year, while the mean unique click rate was 2.8% (3.6% rest-of-year). The click-to-open rate, however, was comparable (14% holiday, 14.8% rest-of-year).

-- Hard bounces, unsubscribes and spam complaints also were lower compared with rest-of-year mailings. Hard bounces were 2.4 times higher in the non-holiday mailing season. Results were closer for unsubscribes (0.10% holiday/0.12% non-holiday) and spam complaints (0.010% holiday/0.014% non-holiday).



Now, do you expect me to conclude that increasing frequency will kill your open and click rates but reduce list churn? Not so fast.  

The "Frequency Math Effect"

Sending more frequently to your database can affect email performance and metrics. Another factor, one that isn't as easily identified, is the Frequency Math Effect. This comes into play when you compare changes on rates (percentages) instead of total or cumulative numbers.

When you increase your email cadence, you increase your total email touches. But, you're also giving your recipients more opportunities to ignore or to unsubscribe from your messages.

Suppose you move from emailing four times a week to daily, or from once a day to twice daily. The total number of emails you send will go up, but you'll normally see a decline in activity rates because your recipients don't usually change their open or click habits at the same pace.

This holds true for list-churn metrics, too. When you increase frequency, your recipients have more emails to act on, whether it means unsubscribing or clicking the "report spam" button. If subscribers aren't opening emails at the same rate they do when you send less frequently, these rates also will go down.

This doesn't mean you should run into your boss's office and brag about how you reduced list churn when you increased frequency, because you would be wrong. You might just be spreading more recipient actions over a larger number of emails. That's the frequency math effect.

Look at the Total, Not Just the Rate

To get a more telling view of email frequency and its effects on performance, add up all email actions (opens, clicks, conversions and resulting revenue, unsubscribes, spam complaints and hard bounces) to get a total number for the entire time period.

Compare this number to a period when you have lower frequency, and you will see whether increasing frequency resulted in more positive email activity, including -- I hope -- higher revenue or conversions. But you will also find that you incurred more list churn through unsubscribes, hard bounces and spam complaints.

The numbers in the chart below show both rates and actual numbers for opens, clicks and unsubscribes generated on higher frequency in the holiday period:

Your Big Question

Are you meeting your business goals (acquisition, conversions, revenue, upgrades, order value or whatever you need to fulfill the plan)? Was the increased revenue worth the tradeoff from higher list churn?

That's a call only you can make.

Until next time, take it up a notch.

4 comments about "Understanding The Email 'Frequency Math Effect'".
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  1. Neil Mahoney from Mahoney/Marketing, July 14, 2016 at 4:41 p.m.

    Too many emails can make you a pain in the neck. 

  2. Loren McDonald from IBM Marketing Cloud replied, July 14, 2016 at 4:59 p.m.

    Neil, frequency isn't really the problem, it it the lack of value in the emails that is the problem. 

  3. Pete Austin from Fresh Relevance, July 15, 2016 at 4:38 a.m.

    @Loren. I agree with your basic premise that higher frequency is better if it significantly increases total responses, and that it's the value in your emails that matters. But these are not separate things - increased frequency decreases value. For example, suppose I offer you a free premium ice-cream: that's a good thing with high vaue, right? But suppose I keep offering you another, and another, and another: the value drops with repetition and eventually you get annoyed and hate me and my ice-creams.

  4. Loren McDonald from IBM Marketing Cloud replied, July 15, 2016 at 12:24 p.m.

    Pete, I did not make the argument that higher frequency is better simply if if increases total responses - that is a call I'll leave to individual brands. My point was just to explain the math behind why most brands see lower "rates" when they increase frequency. But that they need to understand that for list churn metrics like unsubscribes, for example, a lower rate isn't necessarily a good thing - as they are likely losing a lot more subscribers. Increasing frequency by itself is not a bad thing - it is about the value. In your example, the subsequent emails actually aren't of value and so therefore that increased frequency is simply bad email marketing. You can't blame that on frequency - that is the marketer's fault. The problem in email marketing of course, is that in practice, most brands don't increase value when they increase frequency - so we've given increased frequency a bad name.

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