Most of the aggregate data used in this chapter come from the OECD Economic Outlook No. The overview of the labour market impacts of the 2008-09 recession in this section of the chapter makes use of a common dating scheme based on average developments for the OECD area. The more detailed analysis of labour market adjustment in Section 2 makes use of country-specific dating that takes account of differences in when the recession began and ended in different countries. These estimates are based on national definitions of unemployment that differ from the internationally harmonised definition in some countries.