One asset group can quietly become your whole PMax campaign

A Performance Max campaign is built from asset groups, and the campaign-level report shows one blended result even when the asset groups underneath it behave completely differently -- one dominating spend, others barely touching the budget.

Two separate patterns

Concentration is the first pattern worth naming: when a single asset group takes over most of a campaign's spend, that is the exact opposite of what spreading budget across asset groups is meant to protect against, even while the campaign's headline number looks unremarkable.

Waste is the second, more direct pattern, and it is a separate question from concentration: an asset group can carry sustained, real spend with zero conversions for the same window a concentration check would look at, sitting inside a campaign total that still looks fine.

A worked example

Illustrative case: a PMax campaign with four asset groups reports a healthy blended CPA for the quarter. Broken down by asset group, one group absorbs 70 percent of total spend -- concentration worth naming on its own -- while a second, smaller group has spent a real, non-trivial sum with zero recorded conversions across the same three months. Neither pattern shows up in the campaign total, because the first group's strong performance and the second group's small budget share both mask the underlying issue at the blended level.

Why it goes unnoticed

Performance labels and asset-group spend are both visible in Google's own interface, but rarely checked together against the campaign's own history -- which is exactly why either pattern can run for a full reporting cycle before anyone notices.

The two patterns need separate fixes

Concentration and waste look similar on a dashboard -- both sit inside a campaign-level number that still reads as fine -- but they call for different responses. Concentration is a rebalancing question: is the dominant asset group actually earning its share, or just holding it by default. Waste is a pause-or-fix question: does the zero-conversion asset group have a real, fixable problem, or should the budget it holds go somewhere already proven to convert.