“…The selection of data sources was largely based on data availability in relation to the indicator utilised here. The data sources can be considered as reliable, which is evidenced, for example, by their wide use in earlier academic literature (e.g., Perkmann, 2003;Roediger-Schluga and Barber, 2008;Hansen, 2013;Nauwelaers et al, 2013;Makkonen, 2015Makkonen, , 2016Morescalchi et al, 2015; Since many KBUD elements are not only dependent on the city itself but also on the conditions of the larger regional level where the city is situated (Esmaeilpoorarabi et al, 2016), for example, Helsinki and Copenhagen cannot functionally be delineated from their surrounding capital metropolitan regions. Thus, the data was collected for two case study regions including the central cross-border twin city pairs and their surrounding regions: Helsinki (Uusimaa) -Tallinn (Harju) and Copenhagen (Hovedstaden) -Malmö (Scania).…”