Disclaimer, authorship and acknowledgements
This report was commissioned by Arcadis and informed by research produced by the Centre for Economics and Business Research Ltd (Cebr), an independent economics and business research consultancy established in 1992. The expert commentary was compiled by a cross section of Arcadis city and sustainability experts. The views expressed herein are those of the authors only and are based upon their independent research. While every effort has been made to ensure the accuracy of the material in this document, neither the Cebr nor Arcadis will be liable for any loss or damages incurred through the use of this report.
Data is constantly changing. Both Cebr and Arcadis have made every effort to ensure the quality and accuracy of the data. Cebr used its vast databases and connections to compile the data from globally credible sources (e. g. the World Health Organization, CDP, Siemens etc.) Most sources are publicly available. With Arcadis wanting to include 100 cities in a global report, we had to use a data set that could be comparable. There are a lot of varied data sources around the world. Finding like-for-like data for all 100 selected cities limited our selection of sources. Some geographies or cities that did not have sufficient, comparable data were excluded. We focus on data and sources that are credible, comparable and valid. City-level data was used wherever possible, though in some cases only national-level data exists. Where there is no comparable city-level data across countries, the national value is taken, and a national database is used to scale the cities so that they were given a spread around the national average.
The Sustainable Cities Index is constructed by a three-stage averaging process. Some of the indicators are composites, meaning these take an average of their component sub-indicators. In most cases this is the simple average, however given the importance of housing costs to household spending the affordability index was weighted 70:30 in favor of housing. The three sub-indices are calculated by taking weighted averages of their component indicators and the overall score is calculated by taking the simple average of the three sub-indices.
Even where there is no weighting system applied, since the number of indicators differs across subindices, the weights in the overall index do implicitly differ. The same applies for the sub-indicators: two components which go into one indicator will naturally have half the weight of another indicator within the same pillar which has only one component.
The averaging process demands that the scores be converted into common units, for which we use percentages. Each is scaled such that the worstperforming city receives 0% and the best performer receives 100%. Since the sub-indices and the overall index are simply averages of the indicators, they are also measured in percentage terms.
Several of the indicators have outlying values these are defined as observations two standard deviations away from the mean. These are given the maximum or minimum score, as appropriate, and the nexthighest/lowest value is defined as the boundary observation which is used to calculate the the other values.
In 2018 we have revised the calculation of the indices to give greater emphasis to the capabilities of cities. We use the adoption of digital solutions as a proxy measure for the pace at which cities are equipping themselves to meet future needs. Connectivity, citizen engagement and disaster management are all areas where the adoption of new digital solutions will enable cities to accelerate their sustainable development.
1 The Weighting used for each indicator are shown in the table.
