What it is
Attach rate = (buyers of B who also bought A) / (buyers of A).
For consumer markets, the comparison that matters is cross-country attach rates for the same category pair. If UK photo printer attach to mirrorless camera owners is 2.2%, and Germany is 1.0%, that's a structural gap to investigate — not a coincidence.
Why it matters strategically
A single attach rate number can rewrite a category strategy.
The Canon PRO-310 (pro photo printer) analysis hinged on one observation:
- DE: 233K mirrorless camera buyers, 2,349 pro printer buyers → 1.0% attach
- UK: 107K camera buyers, 2,303 printer buyers → 2.2% attach
Same product, same brand share, same retail prices. Germany has 2× the camera installed base — but UK converts 2× more of them into printer buyers.
This reframed the German strategy entirely: the question wasn't "how do we take share from Epson" (Epson was declining anyway). It was "how do we make the German market behave like the UK market" — which led to channel analysis, brand search analysis, and ultimately the awareness investment recommendation.
How Theia computes it
For 1P consumer brands (Canon, Bose), attach can be computed directly from customer-level sales:
- Vendor Central daily ordering data
- Canon internal sell-through
- Loyalty/registration data where licensed
For 3P market views (research firms, PE diligence), attach is approximated from:
- GfK or Stackline category-level penetration
- Survey panels for cross-category buying behaviour
- Search behaviour proxies (do "mirrorless camera" searchers later search "photo printer"?)
The exact methodology depends on data availability per market, but the strategic insight is the same: compare attach across geographies to find structural gaps.
Three classic attach-rate stories
01 — UK printer attach 2× DE. Channel breadth driving awareness, driving cross-category conversion.
02 — JP camera lens attach > 4× UK. Mature photography culture, premium-led buying. Different strategy needed per market.
03 — DE inkjet ink attach lower than expected. Genuine vs compatible ink dynamics — German consumers buy compatible at much higher rates, depressing genuine attach.
Each story is a category strategy. None of them shows up in single-country dashboards.
When attach matters most
- Multi-country brand planning: where are we under-converting our installed base?
- PE diligence: is the category structurally underdeveloped (good) or saturated (bad)?
- Bolt-on M&A: does the target unlock attach for our existing portfolio?
Related concepts
Related terms