Marketing Mix Modelling is a decision-making tool, not a justification tool

If someone asked what Marketing Mix Modelling (or MMM) is for, many marketers would say something like, “measuring ROI and understanding which channels work”. For example, which activities contributed to sales? What return did they generate? Where did marketing make a difference? These are useful questions, but they are not the most important ones.

The real value in Marketing Mix Modelling is not understanding the past, but about helping marketers make better decisions about where, how much and why to invest.

Despite being flooded with dashboards, marketers still lack the confidence in making their next investment decision. So why is there such a gap between having the data and knowing what to do about it?

Stop proving yesterday was right

Too often, marketing becomes an exercise in defending decisions already made. Once the campaign has run and the budget has been spent, the analysis is expected to show it worked.

There is nothing wrong with accountability and understanding whether an investment delivered value, as this is how marketers can learn; however, when marketing analysis is performed as a justification tactic, it risks discovering the very finding that was already believed. Performing this exercise will not move the business forward.

Good Marketing Mix Modelling should be willing to interrogate and challenge an established plan and not merely endorse it. Therefore, the best way to judge the effectiveness of Marketing Mix Modelling is not by how reassuring the findings are, but by whether they improve the next decision.

More measurement doesn’t mean better marketing decisions

Marketing has never had more data or dashboards, yet this doesn’t necessarily create confidence about where to invest. For example, a business can know the reported return on every channel yet still be unsure what to do next.

The fact is that multiple factors affect sales, including pricing, seasonality, distribution, competition, and economic conditions.  Understanding marketing’s contribution requires separating these influences as carefully as possible. Turning those findings into action then requires something more: having the commercial judgement to understand what the evidence suggests doing differently.

The trap of chasing the highest ROI

One of the easiest mistakes in marketing measurement is assuming high ROI and growth decisions are synonymous. Imagine channel A delivers an ROI of £8 for every £1 invested and channel B delivers only £4.

On the face of it, the answer looks obvious: invest more in channel A. However, what if channel A has already been heavily developed and most of the opportunity has already been captured, while channel B still has significant room to grow? The most efficient channel is not always the most expandable one.

The highest historical ROI is not necessarily the best growth opportunity, nor is maximising ROI itself always the right objective. A business can improve its ROI ratio by cutting investment while giving up profitable growth, for example. Growth doesn’t come from investing in what worked yesterday, but what creates value tomorrow. Therefore, the role of Marketing Mix Modelling is not simply to identify winners and losers, but to understand where future growth is most likely to come from.

So, how can marketers put Marketing Mix Modelling into practice? A better investment decision rests on three questions.

1. Where does marketing make a material difference?

Not every positive result deserves equal management attention. One channel might deliver an impressive return on a tiny budget while another makes a much larger contribution to total sales or profit.

The point is not to dismiss smaller activities. Some may offer substantial future potential. It is to distinguish results that are analytically interesting from opportunities that matter economically, either now or at a scale the business could realistically achieve.

The first test is therefore to assess how much value an activity creates, or could create.

2. Where is the headroom to create more value?

A channel can have a strong track record yet limited capacity to deliver additional growth. As investment rises, marginal returns often decline. This means that reaching more people, more often, does not produce proportionate gains indefinitely.

Conversely, a channel with a less impressive historical ROI may have considerable untapped potential. Understanding headroom means looking beyond the contribution already achieved to assess how much more an activity could plausibly deliver, given audience, demand and practical constraints.

The next test is to assess how far this opportunity could realistically grow.

3. What will the next unit of growth cost?

This is where marginal returns matter. Average ROI describes the return on investment already made, and marginal ROI estimates the return on the next increment of spend. The two can be very different.

For example, a channel delivering a historical 5:1 return could produce much less from its next £100,000. Whereas another with a lower average return could produce more from the same additional investment. And because sales are not the same as profit, the comparison should ultimately consider contribution margins and the cost of generating growth, not revenue alone.

The useful question is not “Which channel won last year?” but “Which feasible investment is most likely to create the greatest additional economic value?”

From analysis to action

None of this means past performance is unimportant; it is the evidence that enables better decisions. But the measure of a successful Marketing Mix Modelling programme is not just the quality of the model or the precision of its ROI estimates. It is the quality of the decisions those insights enable, and whether those decisions are put into practice.

The ultimate test of Marketing Mix Modelling is not whether it tells you that yesterday’s choices were right; it is whether it helps you make tomorrow’s choices better. If Marketing Mix Modelling merely confirms what you already believed, it may function as a justification tool, but if it challenges assumptions, identifies material opportunities, and changes how investment is allocated, it becomes something far more valuable: a tool for growth.

If you want to use Marketing Mix Modelling as a decision-making tool, please contact the MetaMetrics team.

Article by Philip Gaudoin | Managing Director, MetaMetrics