Attribution models determine which channel is credited for a conversion when a customer came to the website multiple times and by different paths. The most widespread model, last click, attributes everything to the last source, thereby systematically overvaluing channels that catch the customer right before purchase, typically branded search, and undervaluing those that first informed them about the company. Other models split the credit evenly, with emphasis on the first contact, or data-driven according to users' actual paths. No model is correct on its own – it is a perspective, not the truth. It is therefore recommended to compare results across several models and, for larger budgets, to verify a channel's contribution with an experiment that shows the real incremental effect.
See also: Incrementality, Conversion window, Media mix modelling.
