Do you know which half of the budget is working?

Because each platform claims every conversion it touched, so a single sale that saw a paid social ad, a search ad and an email is counted three times. Platform reporting is useful for optimising within a channel and unusable for allocating budget between channels; that requires a single reconciled source and incrementality testing.

Withholding marketing from a comparable group — usually by geography or by audience — and measuring the difference in total revenue rather than in attributed conversions. It is the only practical way to answer whether spend caused sales or merely accompanied them, and it routinely shows that some well-reported campaigns were taking credit for demand that already existed.

It helps where browser restrictions and consent handling are materially degrading data quality, which for most consumer businesses is now the case. It is not a way to avoid consent requirements — data collected without a lawful basis is a compliance problem regardless of where it is collected — and it adds infrastructure to maintain, so it should be a considered decision rather than a default.

Few enough that every one changes a decision. In practice that is usually a handful: qualified leads or orders, cost per acquisition, contribution after marketing cost, and one or two leading indicators per channel. Reports grow because removing a metric feels like hiding something, which is how they become unread.

For traffic and on-site behaviour, generally yes. For deciding budget it is not, because it cannot see offline conversions, cannot resolve what advertising actually caused, and degrades as browser and consent restrictions tighten. It works as one input alongside CRM revenue and incrementality testing, not as the single source of truth.

By passing offline outcomes back into the measurement: CRM stages, call tracking, and revenue imported against the source that generated the enquiry. For businesses where the sale happens weeks later on a phone call, this is the whole job - and it is why online-only dashboards so often show marketing failing at exactly the businesses where it is working.