Adstock

In one line

Adstock is the carryover effect of an ad — impact that doesn't stop the day it ran, but decays gradually over days or weeks.

Why it matters

Conversions don't always happen the moment someone sees an ad. Ignoring adstock misattributes late conversions to the wrong time or channel. Marketing Mix Modeling (MMM) transforms raw spend into adstocked spend (past spend decayed and added to today's) to avoid this distortion.

In practice

• Brand awareness campaigns tend to have longer adstock (effect lingers).
• Direct-response promos tend to have shorter adstock (effect fades within days).
• Ignoring adstock and just regressing daily spend against daily revenue tends to underestimate true ad effectiveness.

Go deeper

See how adstock is used in real channel-contribution analysis in What is MMM.