Data for OECD countries is taken from the Productivity Statistics Portal section of the OECD web site (http://www.oecd.org/std/productivity-stats/). GDP per hour worked, for the most recent year, is estimated using GDP at current prices ($ US) and Purchasing Power Parities (PPP).
The OECD only provide a figure for the UK. In order to estimate labour productivity in Scotland, figures on Scotland's output per hour worked relative to the UK, which are produced by the Scottish Government as part of the Scottish National Accounts Programme, are required.
The role of purchasing power parity (PPP) in calculating international comparisons of labour productivity is to convert countries' national currencies into a common currency (here, US$) in order to account for differences in price levels between countries. This allows for comparisons in performance to be made across countries.
Labour productivity data are provided annually by the OECD. When this indicator was developed the OECD productivity database only provided productivity levels for the most recent year. Levels in earlier years are therefore estimated using the OECD’s productivity growth series for each member country. This OECD productivity database can be found at, http://stats.oecd.org/WBOS/index.aspx.
Previously, the only official statistics estimates of productivity for Scotland have been produced by ONS, based on Regional Accounts GVA and Regional Labour Market Statistics. However, as of 23 April 2014 official estimates of labour productivity from the Scottish National Accounts Programme have been available which report productivity on a consistent basis with the GDP figures used for other indicators. http://www.gov.scot/Topics/Statistics/Browse/Economy/SNAP/expstats/Productivity.