Somewhere in a boardroom right now, someone is presenting a slide that says the campaign reached 4.2 million people and generated 890,000 impressions.

Everyone in the room will nod. Some of them will write those numbers down. The slide will advance, and nobody will ask the one question that matters:

So what?

We are drowning in data and starving for insight. The rise of digital advertising gave marketers access to more information than any previous generation of the profession had ever dreamed of—and in a move of spectacular collective irony, most of us responded by tracking everything and understanding almost nothing.

This piece is not an attack on data. Data is good. Measurement is good. Accountability is good. But there's a difference between measuring things and measuring the right things. And right now, most marketing reports are measuring the wrong things—or worse, measuring the right things incorrectly.

Let's talk about what actually matters.

The Problem with ROAS and What It's Hiding from You

Return on Ad Spend is the metric that ate the marketing industry. Ask any performance marketer what success looks like and the answer, nine times out of ten, will involve ROAS.

Here's what ROAS actually tells you: for every pound you put into the machine, you got X pounds back. That's it. That's the whole story.

Here's what ROAS doesn't tell you: whether those conversions were from new customers or existing ones. Whether the customers who converted once ever came back. Whether your ads are running in a channel where your competitors are suppressed, making your performance look stronger than it actually is. Whether your attribution model is giving credit to the last click even though the customer touched seven different channels before they bought.

ROAS is a snapshot. Business is a film. And making decisions based exclusively on ROAS is like navigating a city using only the last photo you took rather than an actual map.

ROAS is a snapshot. Business is a film. Don't confuse the two.

High ROAS from repeat customers feels good in the short term. It's actually a warning sign—you're spending money to recapture people who were already yours. High ROAS from a single channel feels like efficiency. It might be fragility—one algorithm change and your numbers collapse.

ROAS is a useful signal. It's a terrible north star.

The Metrics Our Team Actually Watches

1. Customer Acquisition Cost — Segmented

Not overall CAC. Segmented CAC. What does it cost to acquire a new customer from paid social? From search? From influencer? How does that compare to the lifetime value of customers from each of those channels?

Some channels are brilliant at cheap acquisition and terrible at acquiring customers who stay. Some are expensive up front and exceptional at attracting loyal buyers. You need to know which is which before you decide where to put your budget.

2. New Customer Rate

What percentage of the conversions in any given period are from people who've never bought from you before? If that number is below 30% for a growing brand, something is wrong. You're not acquiring—you're retaining, and you're paying acquisition prices to do it.

New customer rate is the health check that most performance reports skip entirely. Add it.

3. Contribution Margin, Not Revenue

Revenue is vanity. Contribution margin is sanity. A campaign that drives £100k in revenue but costs £90k to run, once you account for ad spend, shipping, fulfilment, and returns, is not a successful campaign. It's a very expensive way to break even.

Know your margins. Build your targets around them. Every KPI in a campaign should ultimately trace back to a number that matters to the business—and that number is never revenue in isolation.

4. Blended CAC vs Channel CAC

Here's a number that reveals everything: your blended CAC—total marketing spend divided by total new customers acquired—compared to your channel-specific CAC.

If your blended CAC is £40 and your paid search CAC is £28, you might think search is killing it. But if you dig deeper and find that half of those search converters were already in your email list and were going to buy anyway, you've been giving search credit for work it didn't do.

Multi-touch attribution is imperfect. But it's significantly less imperfect than last-click. If you're still using last-click attribution in 2025, you're making decisions based on a story that you yourself have decided is too simple to be true in any other area of your life.

5. Time to Second Purchase

This is the metric that separates the brands that grow from the brands that churn. How long does it take, on average, for a new customer to come back and buy again?

If your time to second purchase is eight months, your retention strategy should probably start on day one, not month seven. If your time to second purchase is three weeks, you have a different kind of opportunity: a customer already in the habit of engaging with you. Use it.

When a Campaign Needs to Grow Up Fast

You know the situation. Performance has plateaued. The team is pushing for more budget. The algorithm keeps telling you it needs more spend to optimise. And the numbers that looked great in month one haven't moved in three.

The instinct is to spend more. Often the answer is to understand more.

Pull your new customer rate. Is it declining? You're not reaching new people—you're just retargeting the same pool more aggressively. Pull your contribution margin by channel. Where is the money actually coming from, and what's it actually costing? Run a holdout test. Switch off one channel for a defined period and see what actually disappears from your revenue. The answers are almost always surprising.

Performance marketing works. It works extraordinarily well when the inputs are right, the attribution is honest, and the metrics are connected to business outcomes rather than dashboard aesthetics.

The campaigns that grow up fast are the ones built on clarity, not confidence. There's a difference.

Know which one you're working with.