What it means
MMM regresses your sales against spend, seasonality, price, and external factors to estimate each channel''s contribution and diminishing returns — without tracking a single individual.
Why it matters
As cookies and device IDs disappear, click-based attribution under-counts upper-funnel and offline effects. MMM works on aggregate data, so it survives privacy changes and captures brand, TV, and out-of-home that pixels never could. Increasingly, teams triangulate: MMM for budget allocation, attribution for daily steering, incrementality experiments to validate both.