3 newly available national GDP data sources are used to extend existing national GDP ISIMIP data from 2009 onwards based on matching country-specific national real GDP (PPP 2005 USD) for the year 2009.
In consecutive order we use the Maddison Project Database version 2018 (variable: 'rgdpnapc' and 'pop', unit: 2011 PPP USD), the World Development Indicators (WDI) (variable: NY.GDP.MKTP.PP.KD, unit: 2011 PPP USD), and the Penn World Tables (PWT) version 9 (variable:'rgdpe' and 'pop', unit: 2011 PPP USD) to generate GDP estimates and a country-specific rescaling factor, that transfers 2005 estimates for 2011 PPP USD to 2005 PPP USD.
Data from 2006 onwards is then appended to the previously provided national GDP database.
baseyear for matching was changed from 2009 to 2005 as 2009 data is no observational data but obtained by interpolation with 2010 SSP GDP values. 2005 provides last year with observational data.