Sustainability ranking and improvement of countries

Human society is on a collision course with nature, thus its sustainability is seriously questioned nowadays. To understand this problem better it is essential to define and measure sustainability. In this paper a model that uses fuzzy logic, called SAFE, is used to measure sustainability. The sustainability of a country is based on a multitude of basic indicators. In all 75 indicators for 128 countries are used. This work extends SAFE as follows: (a) The model is amended by an imputation procedure to fill in missing data, (b) the rule bases of SAFE are compiled algebraically, and (c) sustainability thresholds are defined so as to reflect expert opinion and international agreements and norms. Countries are ranked according to their sustainability index. Switzerland and Sweden take the first two places and Mauritania and Sudan the two last ones. A sensitivity analysis pinpoints those basic indicators that affect sustainability the most. Decision makers may focus on these indicators to improve sustainability.