For all variables except R&D expenditure and Number of researchers, the data are prepared by the Bank of Portugal. They are based on the biennial stock survey of inward direct investment, which is conducted in odd years. In 1997, when the first survey was launched, all direct investment enterprises were covered. In the subsequent editions of the survey (in 1999, 2001 and 2003), a sample was taken into account for non-financial enterprises according to the level of significance of both annual flows recorded in the balance of payments and previous stocks. All direct investment enterprises belonging to the financial sector are covered by the FDI survey. The response rate is about 80% for non-financial enterprises. Estimates are made for non-responders according to information reported under previous FDI surveys and/or available in the balance sheets’ report of these enterprises. Indirectly foreign-owned firms are not included.