There is a fundamental difference between empirical regularity and causal explanation.
The evidence behind Double Jeopardy and many of the Laws of Growth is impressive. Larger brands tend to have many more buyers and somewhat higher loyalty. And when brands grow, increases in penetration tend to be much greater than increases in loyalty. I accept that evidence.
But none of it, by itself, tells us what caused the brand to grow.
The private-plane analogy makes the distinction wonderfully clear. Thank you, Dale W. Harrison
Rich people own more private planes than poor people. We could demonstrate that relationship with enormous datasets, replicate it across countries, and find that it holds decade after decade.
It would still be absurd to conclude that buying a private plane explains how someone became rich.
Replication strengthens an empirical regularity. It does not turn correlation into causation.
And this is where I think the debate about How Brands Grow becomes important.
The research shows that brand growth is usually accompanied by substantially greater penetration. Fine. But from this observation we have moved to managerial prescriptions: grow penetration, reach all category buyers, build mental and physical availability.
That move requires another kind of evidence.
The scientific burden changes when we move from “this is what growing brands look like” to “this is what marketers should do to cause growth.”
The causal question remains: What caused more people to choose the brand?
Was it innovation? A new source of demand? Greater relevance? Meaningful differentiation? Distribution? Price? Cultural change? Better product performance? A competitor’s failure? Some combination of these?
Penetration matters enormously. But penetration is where much of growth shows up in buying behavior. It does not, by itself, explain where that growth came from.
That is the distinction I think marketing needs to confront.
The problem with evidence-based marketing is not that it lacks evidence.
It is that we sometimes ask descriptive evidence to do causal work.