Plenty of vendors will happily sell you Marketing Mix Modelling (MMM) as something you refresh weekly – a live dashboard, updated in near real time, telling you how each channel is performing right now. It has the shape of progress. It is, in my view, a route to bad decisions.
Start with the question underneath it: what can a business genuinely change, strategically, on a week’s notice? Almost nothing. A retailer doesn’t rebuild its category priorities on a Wednesday because Tuesday’s numbers moved. A brand doesn’t shift its channel mix because last week’s model run looked slightly different from the week before. Any business that actually ran its strategy this way would be reckless, not responsive – and everyone in the room would know it. Strategy operates on a planning cycle for a reason: the decisions it produces are meant to hold for a quarter or a year, not to be re-litigated every Monday morning.
So if the model itself is being re-estimated weekly, what is it actually doing? Not answering a new strategic question, because a new one hasn’t arrived. It is producing new numbers from noisy, thin, week-on-week data, and those numbers will move – sometimes a great deal – for reasons that have nothing to do with anything real shifting in the market. The result looks precise. It updates, it responds, it has decimal places. None of that makes it accurate. It is false accuracy wearing the clothes of rigour, and the confidence with which it’s usually presented is exactly what makes it dangerous.
This is not a criticism of the statistics. I’d guess most weekly-refreshed models are built on Bayesian methods, and there is nothing wrong with Bayesian MMM – it is a genuinely strong approach, used properly. The fault isn’t in the technique. It’s in the cadence. A statistically sound method, run far more often than the underlying strategic question actually changes, produces numbers that are technically defensible and practically meaningless, and the two get confused constantly.
The right cadence for Marketing Mix Modelling follows the planning cycle it’s meant to serve: the annual reset, the quarterly review. That’s not a limitation of the technique. It’s the technique doing its actual job, on the timescale strategic decisions genuinely operate on.
This is a different question from whether MMM is the right tool at all – see When Marketing Mix Modelling isn’t for you.
If a proposal in front of you promises weekly MMM updates, it’s worth asking what business problem that update cadence is really solving, because it is very rarely yours. Drop a line to hello@themmmdoctor.com.