The 2001 edition of the National Accounts of OECD countries: Main Aggregates, Volume I covers expenditure based GDP, output based GDP, income based GDP, disposable income, saving and net lending, population and employment. It also includes comparative tables based on exchange rates and others based on purchasing power parities. Data are shown for 29 OECD countries back to 1988 in most cases, expressed in national currency, but also in US dollars for gross domestic product and household final consumption expenditure back to 1977. These data are based on the System of National Accounts 1993 (1993 SNA) for a majority of countries, but not all. In this issue, the national accounts for four OECD countries (Japan, New Zealand, Switzerland and Turkey) are still presented on the basis of the 1968 SNA.