The economics of information can be classified into micro information economics, or marketplace uncertainty, and macro information economics, or technological uncertainty. The study of micro information economics has experienced rapid growth, while that of macro information economics has suffered relative neglect. As a result of the impact of modern information technologies, macroeconomic structures are undergoing rapid structural change. The explosion in transborder data flows and the collapse of natural monopolies in telecommunications are evidence that economies are undergoing an information revolution. An algorithm based on input-output economics is given to measure, in a cost-effective manner, the structure and size of the information sector in a macroeconomy. The application of this algorithm could generate databases to provide answers to the unresolved problems of information efficiency, and facilitate formulation of development strategies for an information era.