This paper deals with the problems of assessing the success of the member countries of the international association G20 (the Big Twenty). The process of rating the success of these countries using quantitative and qualitative statistical estimates is presented. The proposed evaluation of countries included in this international association, illustrated by the success rate of each country, which it has achieved by using the best available resources and opportunities: natural, demographic, technological, cultural, educational, and institutional. When calculating the assessment of the success of countries - subjects of international associations - the authors proposed to conduct an indicator-based ranking for each specific indicator. The indicators considered in the paper serve as a basis for determining the place of the country in the modern world economy in accordance with the relevant social and economic aspects. They are directly related to the evaluation of development and welfare of society. Assessment based on combining quantitative and qualitative indicators is presented by the authors in the form of a rating. On the basis of this approach, a Comprehensive success rate of the international association of countries G20 was calculated. Data in rating tables presented in this paper serve as a good empirical basis for judging the success of the countries and possible ways of their socio-economic development
