Attribution Model
The rule that decides which touchpoints get credit for a conversion.
An attribution model is the rule that decides how credit for a conversion is shared across the ads and clicks that led to it. Last-click gives all the credit to the final touch; data-driven attribution, now the default in GA4 and Google Ads, distributes it across the path using your account's own data.
It matters because the model changes which campaigns look successful, and therefore where budget flows. Last-click flatters the bottom of the funnel and starves the prospecting that created the demand. No model is perfect, which is why we read campaign attribution alongside the blended, model-free view of MER, the discipline in MER vs ROAS.
Whatever the model, it is only as honest as the data feeding it, so conversion tracking comes first.
Put the number to work: the break-even ROAS calculator turns your margins into the ROAS you need, and a free Due Diligence Audit checks whether the figures you see are the ones you are getting. Back to the glossary.