MostPMaxCampaignsAreJustExpensiveBrandCampaigns
Performance Max claims credit for sales that would have happened anyway. It is often just your brand budget wearing a different costume, and nobody wants to prove it because the results look great.
This is one of the biggest open secrets in Google Ads. Agencies know it. Google knows it. But the conversation rarely happens because everyone benefits from the fiction except you.
The Expensive Costume
Performance Max is positioned as Google's most advanced campaign type. It uses AI to find customers across all Google properties: Search, Shopping, Display, YouTube, Discovery, Gmail.
The pitch: give Google your assets and let the algorithm find the best customers wherever they are.
The reality: the algorithm finds the easiest conversions first. And the easiest conversions are people who were already going to buy from you.
The Performance Max Reality Check
Look at your PMax campaign's "Insights" tab. Check the search themes it is capturing.
If your brand name and close variants dominate the top search themes, PMax is essentially running a branded search campaign with extra steps and less transparency.
The Brand Traffic Reality
PMax campaigns are designed to maximise conversions. The algorithm optimises for this goal relentlessly.
What converts best? People searching for your brand. They already know you, trust you, and intend to buy. These are the easiest wins for the algorithm.
The result: PMax gravitates toward brand traffic because it looks like success. High conversion rates, strong ROAS, efficient spend. But this traffic would have converted anyway, often through organic search or direct visits.
"PMax does not create demand. It claims credit for demand that already existed."
When PMax "wins" a conversion, it often means:
- • A brand search that organic would have captured
- • A direct visit that got intercepted by a display ad
- • A customer in your email list who saw a YouTube ad before purchasing
- • Someone who Googled your exact product name
None of these represent incremental value. You paid for conversions you would have received for free.
Why Nobody Wants to Measure This
Everyone has incentives to maintain the illusion:
PMax captures more spend in a black box format. Less transparency means less scrutiny. If brands realised how much PMax cannibalises, they would spend less.
Agencies
PMax results look excellent on reports. "10:1 ROAS on PMax" sounds impressive, even if half of that is cannibalised brand. Investigating hurts the narrative.
Marketing Teams
Internal teams benefit from strong reported numbers. Questioning PMax performance creates uncomfortable questions about past decisions and budget allocations.
The incentive structure protects the fiction. Everyone wins except the P&L.
Why Incrementality Testing Terrifies Agencies
Suggest an incrementality test to most agencies and watch the deflection begin:
"It's too complex to set up properly"
Translation: We do not want to do it.
"The sample size won't be statistically significant"
Translation: We are creating barriers.
"We might lose momentum during the test"
Translation: We prefer not to know.
"Attribution is too messy to draw conclusions"
Translation: The conclusions might hurt.
Incrementality testing reveals uncomfortable truths. The gap between attributed conversions and incremental conversions can be 30% to 60%. For PMax campaigns heavily weighted toward brand, the gap can exceed 50%.
"An agency that refuses to test incrementality is an agency that suspects the answer will hurt them."
How to Actually Measure PMax Contribution
You cannot rely on Google's reporting to understand true PMax value. Here is what works:
1. Geo-Based Holdout Tests
Exclude PMax from specific geographic regions for 4 to 6 weeks. Compare overall performance (not just paid) between test and control regions. The difference reveals true incrementality.
2. Brand Search Cannibalisation Analysis
Run PMax without brand exclusions for a month, then add brand exclusions. Compare total brand conversions (including organic). If total stays flat while PMax drops, you were paying for existing traffic.
3. Pause Testing
During a stable period, pause PMax entirely for 2 weeks. Monitor overall revenue, not just paid channel performance. If revenue barely moves, PMax was capturing rather than creating demand.
4. New Customer Rate Analysis
Track what percentage of PMax conversions are genuinely new customers versus returning buyers. High repeat buyer rates suggest PMax is remarketing to existing customers rather than acquiring new ones.
What We Typically Find
When we run incrementality analysis on PMax campaigns, the average client is paying for 35% to 55% of conversions that would have happened without the campaign. Some accounts show even higher cannibalisation.
When PMax Is Actually Valuable
PMax is not worthless. It can deliver genuine value in specific situations:
- Low brand awareness: When people do not search for you, PMax's display and discovery placements can build awareness that leads to future demand.
- Product discovery: For brands with large catalogues, PMax can surface products to audiences who would not have found them through search.
- New market entry: When entering markets where you have no existing demand, PMax can help establish presence.
- With proper brand exclusions:When brand terms are properly excluded, PMax can focus on genuinely new traffic.
The key distinction: PMax value correlates inversely with existing brand strength. The stronger your brand, the more PMax will cannibalise rather than create.
An Honest Assessment
We run PMax campaigns for most clients. Sometimes they work brilliantly. Sometimes they are expensive brand protection disguised as performance marketing.
The difference is not the campaign type. It is how honest you are about what it is actually doing.
If your agency cannot explain:
- • What percentage of PMax is brand versus non-brand
- • What the incrementality rate is (even estimated)
- • How PMax performance changes with brand exclusions
- • What the new customer acquisition rate is
Then they are managing a black box, not optimising a campaign.
"The goal is not to eliminate PMax. It is to understand what you are actually buying. That understanding might be uncomfortable, but ignorance is more expensive."
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