Forecasters & trade bodies

Everyone, which is both the appeal and the caution. These are the numbers that appear in trade coverage, board presentations and the article your prospect read last week. Knowing where each one comes from tells you how much weight it deserves.

The agency forecasters — MAGNA (IPG Mediabrands), WPP Media (formerly GroupM) and Zenith (Publicis) — publish to demonstrate expertise and shape the market they buy in. The research firms — EMARKETER — sell subscriptions. The trade bodies — IAB, RAB, TVB, Localogy and the Local Media Association — publish to advance their members' medium.

To size and forecast advertising at national and global level, by medium and channel. The agency houses publish twice-yearly forecasts covering total ad spend and growth by channel. EMARKETER models digital spend by platform, format and audience. The IAB, with PwC, produces the definitive internet advertising revenue report. RAB reports radio revenue, drawing on the Miller Kaplan pool. Localogy and the Local Media Association cover the local marketing services sector and the business of local media respectively.

Varies sharply, and the variation is the point. IAB and PwC collect actual reported revenue from participating digital publishers and platforms, making it the closest thing to audited digital ad revenue. RAB's figures come from Miller Kaplan's reported station pool, extrapolated. The agency forecasts blend their own buying data — a genuinely privileged view — with public disclosures and macroeconomic modeling. EMARKETER synthesizes many third-party sources into a single reconciled estimate rather than collecting primary data.

Forecast figures are stale almost immediately in volatile conditions and are revised twice yearly for that reason. Actual-revenue reports — IAB and RAB — describe a period that has closed and remain accurate indefinitely as history.

The practical failure mode is a number that outlives its context. A growth rate published before a rate shift, an election or a tariff change gets quoted for years afterward. Always cite the release date alongside the figure.

These sources supply the sentence that starts a proposal, and they are free or inexpensive. They also establish the frame your client is already operating in: if a business owner believes everything has moved to social because of a headline, the useful reply cites the same class of source rather than a station's own material.

They should never carry a local argument. A national growth rate applied to a rural county is not evidence, and a sophisticated buyer will say so.

• MAGNA, WPP Media, Zenith — twice yearly, typically around June and December.
• IAB / PwC internet ad revenue report — full-year results in the spring, half-year figures in the autumn.
• RAB revenue — quarterly, from the Miller Kaplan pool.
• EMARKETER — continuous forecast revisions and near-daily analysis.
• Localogy, LMA, TVB — event-driven, around conferences and research releases.

Actual-revenue reports aggregate voluntary submissions under confidentiality, usually with an accounting firm administering the collection, then extrapolate to a total. Forecasts start from a macroeconomic view of GDP and consumer spending, apply historical relationships between the economy and ad spending, adjust for known events such as elections and major sporting cycles, then allocate across channels using observed share trends and, in the agency houses' case, their own forward bookings.

That last input is why agency forecasts are often early to spot a turn and also why they carry an institutional point of view.