Time-decay attribution
Time-decay attribution splits credit for a conversion across the touches before it, giving more credit to touches closer in time to the conversion. The weight usually halves over a fixed interval, called the half-life.
Time decay sits between first click and last click. It accepts that earlier touches mattered but assumes recent ones mattered more, which suits short, considered purchases where the final days of research decide the sale.
A worked example, as arithmetic. A $300 order follows a Meta click eight days before, a Google search click four days before, and an email click on the day. With a seven-day half-life, the weights are about 0.45, 0.67, and 1.0. Scaled to the order, Meta receives about $64, Google about $95, and email about $141.
Like every rule-based model, time decay only divides credit among touches that were observed, and it cannot say whether the sale would have happened without the ads. Google removed it from Google Ads and GA4 in 2023, so running it now means computing it on your own tracking data, ideally next to other models so the disagreement can be read.
Knowing what Time-decay attribution means isn’t the edge.
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