The SSI was initially developed by the Dutch Sustainable Society Foundation, namely by Geurt van de Kerk and Arthur Manuel. Between 2006 and 2016 they delivered the SSI every second year for 154 countries/territories (see here). In 2019 TH Köln took over the responsibility for further development and maintenance of the SSI. We developed the SSI for 2018. As for 2019 we added more countries/territories, i. e. the SSI is now available for 213 countries/territories (see here).
The SSI was audited by the JRC of the EU in 2012. After that minor changes in structure were made. With SSI version 2, we developed the SSI for all years since 2000 for 213 countries/territories. This data collection opens up an opportunity for cross-sectional and longitudinal analyses.
With SSI version 2, users of previous editions will recognize the well established methodology known from earlier editions. Only minor changes were introduced, mostly reflecting variations in data sources. However, expert interviews have not been continued to fill gaps left by data sources. Instead, users will now find blank cells wherever statistical data were not available.