What is adstock?
Adstock is a way of modeling how an ad's effect lingers after it runs. Instead of counting an ad's impact only in the week it aired, adstock spreads that impact over the following weeks, with the effect fading over time.
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How adstock works
Advertising rarely works all at once. Someone who sees a video ad today may search for your brand next week. Adstock gives each period of spend a decaying tail, so part of today's effect is credited to later days or weeks.
The decay rate is usually estimated from your data. A fast decay means the ads work mostly in the moment, and a slow decay means their effect lasts.
Where adstock is used
Adstock is a standard building block of marketing mix modeling. Without it, a model would assume a sale can only come from spend in the same period, which understates channels like TV, video, and brand campaigns.
Adstock is often paired with a saturation curve, which captures the fact that each extra dollar tends to add less than the one before.
Common questions
What is the adstock effect?
The adstock effect is the carryover of advertising impact into later periods. An ad can influence purchases days or weeks after people see it, and adstock models that lag.
What is an adstock decay rate?
The direction depends on the convention. In geometric adstock, A(t) = spend(t) + alpha * A(t-1), alpha is the share carried forward: a higher alpha means a slower fade. If a model instead reports the share lost per period, a higher value means faster decay. Always state the convention.
Do all channels have the same adstock?
No. Channels built around quick action, such as paid search, usually carry over less than awareness channels such as video or TV. A good model estimates adstock for each channel separately.
How is adstock different from a saturation curve?
Adstock describes how an effect spreads over time. A saturation curve describes how returns shrink as spend rises. Marketing mix models usually apply both.
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