IBM Marketing Cloud study.

In IBM Marketing Cloud’s latest benchmark study of e-mail marketing metrics, the firm added a new section on open rates and other data on holiday retail and e-commerce. The holiday data revealed the importance of frequency in e-mail marketing.

IBM found that the unique open rate for retail and e-commerce companies had a mean of 17.6 percent during the holiday shopping season, which compares to a rate of 20.9 percent during other times of the year. The researchers noted that e-commerce and retail marketers step up the frequency of e-mails during the holidays, which can reduce open rates. But that’s not necessarily a bad thing, IBM researchers said in the report.

“During heavy volume time frames, the higher cadence of e-mails typically produces fewer opens and clicks per message sent but more opens and clicks in total,” the authors of the report noted. “This can be attributed to the ‘frequency math effect.’ Think of it like this: Suppose you double your frequency, but see open or click rates going down by 15 to 20 percent from one message to the next. That’s not necessarily reason to panic because during the entire sending period you should have a marked increase in total opens and clicks.”

The report said similarly, retailers and e-commerce marketers “can also expect to see hard bounces, spam complaints and unsubscribe rates decline when you raise frequency, but this isn’t always cause for rejoicing. Instead, frequency math is at work here, too. That’s because you’re likely sending many more messages, so your total list churn over the sending period will be higher.”

Regarding click-to-open rates, or CTORs, for retailers and e-commerce sites, the study found it to be 14.8 percent during the non-holiday period versus 14 percent for the holiday shopping season. “The slightly lower CTORs during the holidays suggest that strong offers and calls to action are performing reasonably well, but that retailers are likely leaving some money on the table,” the researchers said. “With higher purchase rates during the holidays, click-throughs in opened e-mails should be higher. E-mails that lack personalization and undifferentiated offers are likely not motivating enough recipients to take action.”

Compared to other industries, the retail and e-commerce sector has some of the lowest overall open rates. Of the 18 industries tracked in the study, marketing agencies and services as well as media and publishing also have similarly low open rates.