If you only measure response rate, you are grading a week-long relationship on a single handshake. The research on how households actually treat mail shows a much longer, richer engagement than a binary responded-or-not can capture, and modern tracking finally lets you see it on your own campaigns.
What the engagement research measures
JICMAIL, the UK's industry body for mail measurement, runs a continuous household panel and reports that a typical direct mail item is interacted with about 4.5 times, reaches more than one person per household, and stays in the home for around 7.8 days. Their attention study puts total attention per direct mail item at well over two minutes across its life.
Compare that honestly to a display ad measured in fractions of a second, or an email whose entire life is one glance in a preview pane. Mail is not an impression; it is a houseguest.
The engagement signals you can track yourself
Repeat scans. One person scanning your card three times across a week is the household-panel behavior showing up in your own data. I treat repeat scanners as the warmest names on the list, because they are literally picking the piece back up.
Scan timing spread. If scans arrive across ten days rather than one spike, your piece is living on counters, which argues for keeping-worthy creative and patient follow-up windows. Delivery tracking gives you the day-zero anchor that makes this spread measurable.
Multi-person response. Different devices scanning the same household's code hint at the pass-along readership JICMAIL measures, over one person per item. One mailbox, multiple readers.
Call-after-scan. A scan followed by a call from the same area is engagement deepening into intent. With per-campaign call tracking alongside per-recipient QRs, you see both halves.
Why engagement metrics change decisions
Engagement data rescues good campaigns from premature judgment. A drop that looks quiet on day two and compounds through day ten is a keeper creative with a slow fuse, not a failure. It also reframes creative strategy: if the median piece gets multiple encounters, design for re-reading, with an offer that rewards a second look and a deadline that creates a reason to act on it.
Response rate tells you the ending. Engagement metrics tell you the story, and the story is where the next campaign's improvements come from. This layered view, scans, repeats, timing, and calls on one screen, is exactly what we built Relay's report to show.