Which Half? Finding the Marketing Spend That's Working

John Wanamaker supposedly said: "Half the money I spend on advertising is wasted; the trouble is I don't know which half." He said it over a hundred years ago. For most small businesses in 2026, nothing has changed.

Most small businesses can't tell you which of their marketing actually makes money. They spend on what feels active, the channel that's loud, familiar, or that everyone else uses, rather than on what demonstrably pays back. Two numbers cut through it.

"Half my marketing works. I just don't know which half."

The line is a century old, usually credited to the retailer John Wanamaker, and it's still the most honest thing most owners could say about their marketing. Money goes out every month, to ads, a listing, a directory, whoever called offering leads, and revenue comes in, but almost nobody can draw a clean line between the two.

So spending becomes a matter of habit. You keep paying for the channel you've always paid for, the one with the impressive-looking numbers, without ever checking whether it returns a penny of profit. The waste isn't dramatic. It's a steady monthly leak into things that were never working.

Revenue ROAS lies. Profit ROAS tells the truth.

The usual measure is return on ad spend: the revenue a channel brings in for every pound you put into it. A 4-to-1 ROAS, four pounds back for every one spent, sounds like a triumph. It often isn't, because revenue is not profit.

Spend £1,000, get £4,000 of sales: a 4-to-1 return that looks superb. But on a 25% margin, that £4,000 is £1,000 of gross profit, exactly what the ads cost. You broke even, and called it a win.

The fix is to apply your margin and look at profit ROAS: what the channel returns after the cost of actually delivering the sales. On a 25% margin you need to bring in four pounds just to cover every pound of spend, so anything under a 4-to-1 return is losing money. The thinner your margin, the higher the bar. A great many campaigns owners are proud of are quietly running at a loss the moment you do this sum.

The number that decides if growth is affordable

The second number is the relationship between what a customer is worth and what they cost to win: lifetime value against acquisition cost, LTV to CAC. If a customer is worth £300 in profit over the time they stay with you, and costs £200 in marketing to acquire, that's 1.5 to 1, and it's fragile.

As a rough guide, around 3 to 1 is the healthy mark: a customer worth roughly three times what they cost to win. Below that, you're buying customers you can't really afford. Well above it, say beyond 5 to 1, and you may be under-investing, leaving growth on the table. This one ratio tells you, more than any other, whether your whole way of winning customers stacks up.

Why owners get it wrong

The mistakes are consistent. They measure revenue instead of profit, so high-revenue, low-margin channels look better than they are. They don't track where customers actually came from, so they can't tell which spend earned which sale. They judge marketing on vanity, likes, reach, impressions, rather than money. And they keep funding a channel out of habit long after it stopped working. The result is money flowing to the loudest channel rather than the most profitable one.

Move the money to what works

Once you measure profit ROAS by channel and know your LTV to CAC, the decisions stop being a matter of opinion. The pattern almost every business finds is the same: a large slice of the spend is doing very little, and a small slice is doing nearly all the work. The job is simply to see which is which, then act, cut or fix the channels losing money, and put more behind the ones returning real profit.

That's the whole discipline. Not more marketing, and not necessarily a bigger budget, the same budget pointed at what actually pays back.

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Moor & Co helps small business owners turn marketing from a leap of faith into a measured investment. The tools behind it run on [3DMAI](https://www.3dmai.co.uk), whose Marketing Analysis tool shows profit ROAS with your margin applied, and whose LTV:CAC calculator tells you whether your acquisition model is sustainable. [Book a free 30-minute conversation](https://moorandco.co.uk), no commitment, or download the full briefing, Which Half?