You can build a real 4-channel MMM (Marketing Mix Model, 营销组合模型) in a Google Sheet in one afternoon — no Python, no data engineer, no $40K vendor. I walked a DTC client through it last quarter. The build took 3 hours, the adstock decay curves are written by ChatGPT, and the sensitivity test exposed a $14K/month waste nobody had spotted.
Most marketing attribution is a $40K/year vendor contract answering a question you can solve in a Google Sheet. Here are the three models I have built for clients since 2014 — last-click, first-click, and time-decay — with the exact formulas, the column layout, and the one trap that catches every team the first time.
