5. Conclusions and future work
Various frameworks for assessing indicators of city sustainability are employed worldwide, including Urban Sustainability Indicators, Mercer's Quality of Living Ranking, Monocle's Quality of Life Survey, European Green City Index, Quality of Life Index, Global City Indicators Programme, City Blueprint, Indicators for Sustainability, and the EIU's Global Liveability Ranking. These frameworks determine quality of life values in their assessments. Nonetheless, for now, these frameworks for assessing indicators of city sustainability do not provide automated quantitative guidelines for enriching concrete indicators. They are unable to rationalize designated indicators by considering the existing quality of life situation in the city under analysis; they are unable to calculate the values of the indicators which would permit a city to be best of the others under analysis. The INVAR method supplements the frameworks with new above functions.
There is a comparison of the Quality of Life Index and the INVAR method to establish the accuracy of the suggested INVAR method. The assessment of a city's quality of life employs the same 2012–2016 data on European cities (criteria values and weights). Usually all the frameworks for gauging indicators of a city's sustainability have developed ranking grades that are diverse, to some extent.