Total intramural expenditure on research and development (R&D) performed within a country and funded from abroad but excludes payments for R&D performed abroad during a given period, expressed in terms of purchasing power parity USD.

It is often displayed as a matrix of performing and funding sectors. GERD and the GERD matrix form the basis of international comparisons of R&D expenditures. They also provide the accounting system within which the institutional classifications and functional distributions may be applied.