Attribution is hot. For brand marketers, ever concerned about ROI, measuring the efficacy of their campaigns — that is, to tell if they’re actually driving sales — is a constant headache. But how to attribute a sale to a given piece of marketing? It turns out there are many attribution models, which comes as both a curse and a blessing. There are several models: single source, multi-source and the more complicated algorithmic models that recognize the multitude of channels out there.