The 70/30 activation-to-brand split is the number nobody argues for and almost everybody lands on. You get there without deciding to. Every quarter you fund what you can measure and cut what you cannot. Binet and Field put the healthier number nearer 60/40 the other way, brand ahead of activation, but that is a fight for another essay. This one is narrower. If you run an activation-heavy split for eighteen months, what does it cost you, measured in the currency a performance buyer respects, the cost per click?
The mechanism, in one paragraph
Cut brand spend and your share of search falls. Branded clicks are cheap; generic clicks are dear. As the mix shifts from branded to generic, your blended cost per click climbs, and it compounds.
I laid the mechanism out in full in an earlier essay, so here is the short version. Brand spend keeps demand warm, and warm demand shows up as people searching your name. Those branded clicks are the cheapest and highest-converting traffic you own. Cut brand spend and, over a few quarters, your share of category search slips. The searches you have lost were the cheap ones, so you replace that volume on generic, non-brand terms, where you bid against everyone and every click is someone who has never heard of you. Your blended cost per click rises. The auction has not turned against you; your mix has moved from cheap traffic to dear.
The eighteen-month arithmetic
An illustrative model: hold this split for six quarters and a plausible chain of small declines compounds into a blended cost per click meaningfully higher than where you started.
Put rough numbers on it. This is a model, not a measurement. Watch the shape of the line and ignore the exact decimals. Say branded search is 40% of your clicks today at £0.30 each, and generic is 60% at £1.80. Your blended cost sits around £1.20. Now run this split for six quarters. You lose a few points of share of search a quarter, so branded volume falls from 40% of the mix toward 28%. Generic makes up the gap. Nothing dramatic happens in any single quarter. But the branded share is the cheap share, and as it shrinks, the blended cost rises with it. By month eighteen the same clicks cost closer to £1.45, a fifth more, for demand you used to get for less.
The exact curve is yours. Pull your branded and generic click shares and their average costs, decide how fast your share of search is moving, and run the same blend forward. The number that comes back is not a forecast you should trust to the penny. It is a floor on the cost of the split, because it only counts the auction effect and ignores the conversion-rate drag that a colder audience adds on top.
The branded share is the cheap share. Lose it and the blend gets dearer, quarter after quarter.
What the number leaves out
The chart only counts the auction effect. It ignores the conversion-rate drop from colder traffic, and the fact that rebuilding share of search takes far longer than losing it. The real cost is higher than the curve.
Two things make the true cost worse than the chart. The colder generic traffic converts worse than the branded traffic it replaced, so the same spend buys fewer customers before the cost per click even moves. And the timing is not symmetrical: losing share of search takes quarters, winning it back takes years, because you are rebuilding demand from a lower base. So the eighteen-month figure is not the bill. It is the deposit on a longer one.
Where this sits on the triangle
The 70/30 split is the Activation corner over-funded and the Equity corner underfunded. The rising cost per click is the invoice, paid in the metric the split was meant to protect.
On the model, a 70/30 split is a brand parked hard in the Activation corner. The rising cost per click is what the starved Equity corner sends back, and it arrives in the one place the split was supposed to be efficient. You cut brand to protect performance, and eighteen months later performance is the thing paying for the cut.
So run your own eighteen months before the next planning round. If the cost-per-click line bends up, the split is the reason, and more budget at the same split does not flatten the line. It only buys the bend more slowly.
Notes & references
- Les Binet & Peter Field, The Long and the Short of It (IPA, 2013), on the roughly 60/40 brand-to-activation split. On my reading list.
- The full auction mechanism (Quality Score, branded search, share of search, conversion rate) is in Your CAC keeps rising because your brand is weak.