Nobody has ever perfectly measured marketing ROI. Anyone who tells you they have is either lying or stupid.
For my entire career, I've been sold a succession of silver bullets promising to solve the measurement puzzle. From coupon codes in the back of magazines to the multi-touch attribution models that clog up our CRMs, each promised a direct line of sight between spend and return. Each has been a partial lie.
We've lived through three distinct eras of marketing measurement. First was the age of Print, an era of expensive ambiguity. Then came the Pixel, which offered the illusion of perfect precision but created a generation of marketers who can't see the wood for the trees. Now, we are entering the age of the Prompt — an era of predictive, agentic execution that will make the first two look primitive. Most agencies and marketing teams are utterly unprepared for it. They are still celebrating the precision of the pixel, blind to the fact the game has already changed.
The Print Era: An Age of Expensive Ambiguity
Early in my career, measurement was a dark art. We'd spend a fortune on physical media and hope for the best. A full-page advert in The Times could set a client back £50,000, and the only 'data' we'd get back was the publisher's claimed 'readership' figure and a vague metric called 'opportunity to see'. It was glorified guesswork, propped up by expensive lunches and confident-sounding media buyers.
Metrics were outputs, not outcomes. We measured column inches, airtime minutes, and the estimated size of the audience. The connection to an actual sale was a matter of faith. Did the phone ring more than usual the week the ad ran? Did footfall seem 'up'? It was a joke.
Here’s my contrarian take: this ambiguity wasn't all bad. The very impossibility of granular measurement forced marketers to focus on what actually matters in the long run: building a powerful, memorable brand. Without clicks and conversions to obsess over, the core job was to create an ad so compelling, so creative, so culturally resonant that it would lodge itself in the public consciousness.
Think of the Guinness 'Surfer' ad or Cadbury's 'Gorilla'. These weren't designed to drive immediate clicks. They were designed to build feeling, to create a deep-seated brand preference that pays dividends for decades. The lack of minute-by-minute data forced a focus on the big picture. That discipline has been largely lost. The pixel killed it.
The Pixel Era: The Illusion of Perfect Measurement
The arrival of digital, and with it the tracking pixel, felt like a revolution. We traded billboards for banners and readership for reach. Suddenly, we had an alphabet soup of metrics at our disposal: CPC, CTR, CPA, LTV, ROAS. We could track a user from their first click on a Facebook ad, through to their website visit, and all the way to their final purchase. Or so we thought.
This ushered in the age of performance marketing. Everything became about direct response. If we couldn't measure it, we didn't do it. Brand-building was derided as fluffy and unquantifiable. The only thing that mattered was the last-click attribution figure at the bottom of the Google Analytics report.
Last-click attribution is the original sin of digital marketing. It assigns 100% of the credit for a conversion to the final touchpoint the user interacted with. It’s simple, clean, and completely wrong. It tells you what closed the sale, but nothing about what created the demand in the first place.