Why retention is a measurement problem before it is a marketing problem
Most direct-to-consumer brands treat retention as a campaign question: which offer, which channel, how often. That is the last question, not the first. The first question is whether you can see what is actually happening, and most brands cannot, because they look at a blended repeat purchase rate.
A blended rate is the share of all customers who have ordered more than once. It improves automatically as your customer base ages, because customers acquired two years ago have had two years in which to order again. It can rise steadily while every customer you acquired this quarter is performing worse than any cohort before them. It is, in other words, a number that reliably tells you something reassuring and occasionally tells you the truth.
Read by cohort instead
Group customers by the month of their first order. For each group, track what share had placed a second order after thirty days, sixty days, ninety days, and so on. Now you can compare like with like: the ninety-day figure for the January cohort against the ninety-day figure for the April cohort.
This one change usually reframes the conversation entirely. Brands that thought retention was improving often find that it was flat and that the blend was doing the work. Brands that thought a channel was performing well often find it acquires customers who never return, which means the acquisition cost was worse than reported.
