Adela Mincea
The problem with blended numbers
The blended ROAS in your account is an average. Averages combine things that should not be combined. A healthy number at the account level can mask unprofitable spend at the campaign level, and budget gets allocated to the average, not to the economics underneath it.
There is a statistical concept called Simpson's Paradox. A trend that appears in aggregate data disappears, or reverses, when the data is broken into subgroups.
Marketing accounts produce a version of this problem constantly. The blended ROAS looks healthy. The component parts tell a different story. Budget is allocated to the blend. The component parts determine what the business actually returns.
What the average hides
A Google Ads account spending $15,000 per month shows a blended ROAS of 4.2x. By most benchmarks, that reads as a performing account.
Break it down by campaign type:
- Branded search: $2,000 spend, 11x ROAS
- Generic search: $4,500 spend, 3.8x ROAS
- Performance Max: $6,000 spend, 3.1x ROAS
- Prospecting display: $2,500 spend, 1.1x ROAS
The blended 4.2x is accurate. It is also a mathematical artefact that obscures the fact that $2,500 per month, one sixth of the total budget, is operating at a ROAS that, on a 28% gross margin, is deeply unprofitable. Breakeven at 28% margin is 3.6x. The display campaign at 1.1x is losing money on every attributed conversion.
The account looks healthy. One campaign is a problem. The average conceals it.
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Why averages are structurally misleading for budget decisions
Budget allocation follows performance signals. If the account shows 4.2x, the instinct is to increase budget to the account, or at minimum, to maintain current allocation.
But budget does not go to the account. Budget goes to campaigns. When you increase account spend by 20%, the increase gets distributed across campaigns proportionally or according to automated bidding. The 1.1x campaign grows alongside the 9x campaign.
Every dollar added to the account is divided across all the underlying economics. The average looks stable. The actual marginal return on new spend is determined by which campaigns absorb it. Automated bidding systems tend to send incremental spend toward campaigns with volume, not campaigns with margin.
This is how accounts scale in a way that feels productive and deteriorates economically. The blend holds. The composition shifts.
The categories that averages routinely conceal
Branded vs. non-branded split. Branded campaigns capture existing demand at high efficiency. Non-branded campaigns generate new demand at higher cost. Blending them produces a number that overstates the value of non-branded spend and understates the cost of acquiring genuinely new customers. A business making budget decisions on blended ROAS is making decisions based on a number that includes conversions it would have received anyway.
Product categories with different margins. A 4.5x ROAS on a 40% margin product is profitable. A 4.5x ROAS on a 15% margin product is not. When a campaign or ad group promotes both, the ROAS averages across them. The budget decision treats them as equivalent. The margin calculation does not.
New vs. returning customers. Platform attribution often counts returning customer purchases at the same value as new customer acquisitions. A business paying $45 CAC to re-acquire a customer who costs $8 to retain through email has a CAC problem hidden in its acquisition numbers.
Seasonal performance averaged into a stable baseline. A campaign with a 7x ROAS in November and a 1.8x ROAS in March has an "annual average" of somewhere around 4x. Budget set to that annual average is over-invested in March and under-invested in November.
What disaggregation actually requires
Breaking the average down into useful components requires three things.
Segment by the dimension that matters to the business. For most e-commerce businesses, the relevant splits are: branded vs. non-branded, campaign type, product category margin, new vs. returning customer. Each of these produces a different economic picture.
Apply the right denominator. ROAS alone is the wrong measure for budget decisions because it ignores gross margin. The correct comparison is ROAS against the breakeven ROAS for each segment. A campaign at 3.8x against a product category with 24% margin (breakeven: 4.2x) is unprofitable. That number does not appear in the platform report.
Evaluate marginal return, not average return. The average ROAS across all spend tells you what the existing budget is producing. It does not tell you what additional budget will produce. Marginal return, the return on the next dollar spent, is lower than average return in almost every account, and in some campaigns it is negative while the average holds.
The Google Ads Audit breaks down ROAS by campaign type against your actual margin economics, showing what's profitable, what's borderline, and where the average is covering a problem.
See what the audit covers →The decision that follows from this
Once the account is disaggregated, the budget decision changes.
The question is no longer "should we increase total spend?" The question becomes: which segments are operating above breakeven margin-adjusted ROAS, what is their capacity for additional spend before returns diminish, and which segments are operating below breakeven and should not receive additional budget regardless of how the blend looks?
These are different questions. They produce different answers. They require working from the component economics rather than the aggregate.
Most accounts are managed at the aggregate level because that is how platforms present data and how most reporting is structured. The aggregate is useful for a quick read on performance. It is not useful for budget decisions, because budget does not flow to the aggregate. It flows to the components.
The average is real. It is also the least informative number in the account for the decision that matters most.
Adela Mincea is a Marketing Economist based in Cluj-Napoca. The Google Ads Audit covers margin-adjusted ROAS by campaign type, spend allocation against unit economics, and a verdict on what the account is actually producing. $499, delivered in 3–5 business days.
Adela Mincea is a marketing economist, paid media strategist, and certified trainer. She helps growing businesses make marketing profitable before scaling it by validating margins, acquisition economics, and pricing power before deploying paid media and AI-enabled systems.
Adela Mincea
Marketing Economist
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