What each model is actually claiming
First-touch claims that discovery is the scarce thing. If nobody had ever heard of you, no later interaction could have happened, so the channel that created awareness earns the credit. Under this model, top-of-funnel spend looks strong and remarketing looks pointless.
Last-touch claims that conversion is the scarce thing. Plenty of people know about you; the interaction that finally produced action is what mattered. Under this model, branded search and retargeting look excellent — even though both mostly harvest demand created elsewhere.
Why first-touch usually fits service businesses better
A roof or a system replacement is considered for weeks. The homeowner sees an ad, mentions it to a spouse, reads reviews, asks a neighbour, then searches the company name and calls. Last-touch hands that entire sequence to branded search, which would have had nothing to harvest without the ad.
First-touch keeps the credit with the spend that actually created the opportunity, which is the spend you have to decide whether to repeat. The trade-off is that it undervalues the follow-up work that closed the gap — which is why the model should be stated, not hidden.
Why multi-touch is often a bad deal
Multi-touch splits credit across the whole path — evenly, weighted toward the ends, or by a fitted model. It is more realistic in principle. In practice it needs enough conversions for the weights to mean anything, and complete identity across every touch, which is exactly what phones, shared devices and word of mouth destroy.
For a business doing a few dozen sold jobs a month, a fractional-credit model produces confident-looking decimals derived from a handful of events. A clearly-labelled single-touch number is more honest and leads to the same budget decisions.
The rule that matters more than the model
- Capture the first touch at entry and keep it; do not let later page views overwrite it.
- Record the converting touch separately rather than replacing the first one.
- Report one model as the default, and be able to show the other on request.
- Never compare a first-touch report from this quarter to a last-touch report from last quarter.