How much is spent on advertising worldwide each year?

How to get close to this number

Take a share of the world economy. Global output is around a hundred trillion, and advertising runs at roughly one percent of economic activity in developed markets. One percent of a hundred trillion gives a figure around a trillion.

The digital share in the explanation is the structural shift: roughly seventy percent now goes to digital channels, up from almost nothing two decades ago. An industry that funded newspapers, broadcast television and billboards reallocated most of its spending within a generation, and the collapse of those older media follows directly.

The concentration is the part with the most consequences: three companies take over half of the digital total. An advertising market where most spending flows through a handful of intermediaries gives those intermediaries enormous leverage over publishers — which is the context for every conversation about ad revenue, including the ones in this project's own documentation.