Abstract
Motives: The problem of measuring the level of sustainable development is a subject addressed by many authors in their research. Aim: In this article the Authors proposed a new method of classifying objects based on Jenks’ Natural Breaks to measure the level of sustainable development. The analysis was carried out on the basis of the data obtained from Statistics Poland. An important element of the research was the development of the process of selection and rejection of input data on the basis of a variety of statistical indicators. This resulted in a set of data which, on the one hand, is statistically justified and, on the other, describes the examined phenomenon in a comprehensive way. Results: The research objects were 66 Polish district cities; Authors obtained a ranking of cities in terms of its Sustainable Development Level. The authors decided to verify the correlation of the results obtained from a proposed method of classifying objects based on natural breaks, with those from the chosen taxonomic method (Hellwig’s method) and the Classic Ranking. The fact of receiving highly correlated results confirms the validity and reliability of the proposed method.