In recent years, an increasing number of scientific works have analysed or discussed the DESI.

In this regard, a bibliometric analysis based on the Web of Science Core Collection-Clarivate Analytics database was recently provided by Kovács et al. [2022] who classified the literature ¶{p. 186}into three main clusters according to the frequency of keyword co-occurrence. This section provides a qualitative overview of this literature with the main goal of identifying key areas of investigation, prevailing methodological approaches, scrutinised countries and temporal frame of analysis. In this context, we limit our research to Scopus, which is one of the largest citation databases worldwide.

Moreover, since a systematic literature review lies beyond our scope, we decided to limit our analysis only to works that are more likely to be of higher quality as they went through a rigorous peer review process, i.e., published papers and book chapters. We searched for documents which, in the title, keywords or abstract, contained the keyword «digital economy and society index» or «DESI index». We did not apply any filter for the field of knowledge, but limited the search to documents published in English. The query initially provided 60 documents (last update 14 October 2022) that were scrutinised by reading the full paper. After initial screening, 26 works were excluded from the analysis for a variety of reasons, notably: 1) they consider the DESI only as a background/contextual factor, or they provided no original elaboration or analysis of empirical data based on the DESI; 2) they did not match minimum quality standards, in terms of methodological rigour, or are too short; 3) they analysed I-DESI rather than DESI dimensions.

The final sample included 34 scientific works (32 papers and 2 chapters) that are all empirical in nature. As for their time distribution, it can be easily observed that works analysing DESI variables have increased over time from 2017 to 2022, starting from the first few publications in 2017 (n=1), 2018 (n=1) and 2019 (n=2). Since 2020 the number of publications has shown a rapid increase, rising to 7 and 9 in 2020 and 2021, respectively, and even doubling in 2022, with 15 publications on the topic.

As for the geographical area(s) of investigation, the vast majority of works (n. 20) included in our sample used DESI data by considering all EU countries as units of analysis (27 or 28), while in several of them [i.e., Soava, Mehedintu and Sterpu 2022; Endrődi-Kovács and Stukovszk 2022; Pekarcikova et al. 2021; Jaković, Ćurlin and Miloloža 2021] the unit of analysis consists of the firms operating in EU countries. It is worth pointing out that, in some cases, data unavailability constrained the authors ¶{p. 187}to limit their analysis to fewer countries, notably to the 23 OECD EU countries [Başol and Yalçın 2021; Fernández-Portillo, Almodóvar-González and Hernández-Mogollón 2020] or to 21 countries [Ivanović-Dukić, Stevanović and Rađenović 2019]. In this regard, five countries in the Euro-Med cluster were considered as units of analysis, such that empirical insights can be derived about Greece, Italy, Portugal, Slovenia and Spain. In two papers, however, the authors deliberately decided to focus on a restricted number of countries, namely the four countries of the Visegrad Group (V4) in Central Europe [Esses, Csete and Németh 2021] and 13 selected ones [Juhász et al. 2022] that include, among others, the Euro-Med countries of Greece, Croatia and Slovenia. A small number of studies (n. 8) focused, instead, on individual countries.

Overall, however, the countries examined are scant, including Romania [i.e., Claudia and Mihaela 2022; Barna and Epure 2020; Tataru and Fleaca 2020], Poland [Moroz 2017], Hungary [i.e., Endrődi-Kovács and Stukovszky 2022], Slovakia [i.e., Pekarcikova et al. 2021] and only two Euro-Med countries, namely Spain [Czubala Ostapiuk and Solsona 2021] and Greece [Laitsou, Kargas and Varoutas 2020].

The research can also be classified and analysed in relation to its time frame. In this regard, the final sample includes works using both cross-sectional data related to a specific year [e.g., Noja et al. 2022; Liu 2022; Jaković, Ćurlin and Miloloža 2021] and panel data usually related to the temporal window in which DESI data were available at the time of publication [e.g., Imran et al. 2022; Soava et al. 2022; Laitsou, Kargas and Varoutas 2020]. In particular, when data collection and analysis are longitudinal, it is possible to track and ascertain the evolution of the overall digitalization level or specific DESI variables over time [e.g., Firoiu et al. 2022; Kovács et al. 2022; Borowiecki et al. 2021]. It is also worth highlighting that, in almost all papers, the highest level of granularity of the DESI is scantily considered for empirical analysis (i.e., they do not measure values at the level of specific indicators for each DESI sub-dimension).

As for the subject area of publications, although most journals are included, alternatively or simultaneously, in the fields of «social science, business, management and accounting» and «economics, econometrics and finance», there are also works ¶{p. 188}in the final sample published in journals or books assigned to other subject areas, notably «computer science», «environmental science», «mathematics» and «psychology». This wealth of fields reflects the variety of issues that are investigated in the reviewed papers along with the adoption of a multi-disciplinary perspective.

If we examine the issues under investigation, we can identify three main groups of works. There is a first group of works where the empirical focus is on the level of digitalization and/or the temporal evolution of digitalization processes in one specific country, in a sub-group or, in most cases, in all EU countries. Interestingly, there is one chapter that adopted the guidelines about DESI provided by the European Union to apply this index at sub-country level, that is for the Italian region of Abruzzo [Russo 2020]. In detail, in research interested in the digital performance of a specific EU country, the related dimensions measured through the DESI are compared to the average EU values or ranked in relation to other EU countries [e.g., Claudia et al. 2022; Laitsou, Kargas and Varoutas 2020; Czubala Ostapiuk and Benedicto Solsona 2021; Moroz 2017]. For example, through comparison with other EU Member States, Laitsou, Kargas and Varoutas [2020] identified the areas where Greece shows convergencies and divergencies and also provided a forecast about the impact of current policies on the digital competitiveness of the country. In these studies, measures about the DESI variables subjected to descriptive statistics or basic correlations are usually integrated with secondary qualitative data about the investigated country and are used to enrich and support the interpretation of quantitative data analysis. However, we also found a paper where data about DESI are only used for qualitative SWOT-based analysis focusing on the specific country, without comparisons with other contexts [Tataru and Fleaca 2020]. By contrast, the studies that look at all EU countries address the issues of correlation and causality of the DESI dimensions [e.g., Bezrukova et al. 2022; Juhász et al. 2022; Bánhidi, Dobos and Nemeslaki 2020] or compare, classify and cluster countries according to their digitalization values for one or more DESI dimensions or sub-dimensions [e.g., Firou et al. 2022; Liu 2022; Borowiecki et al. 2021].

In their recent paper, for example, Firou et al. [2022] relied on the available DESI data to group all EU Member States according to the evolution of their digital performance, identifying ¶{p. 189}the main differences and potential areas of development. Bánhidi, Dobos and Nemeslaki [2020] undertook multi-stage research as they first analysed the linear and causal relationship between the DESI dimensions, and then clustered countries and compared them through two different rankings. In all studies, a variety of more advanced inferential and exploratory statistical methods were used, also in combination for data analysis, including cluster analysis [Firou et al. 2022], the co-plot method [Liu et al. 2022], k-means cluster analysis [Jaković, Ćurlin and Miloloža 2021] and multi-dimensional scaling [Bánhidi, Dobos and Nemeslaki 2020] to name a few.

In a second group of papers, the goal is to ascertain the impact of digitalization on one or more dimensions related to the environmental, economic, social and/or human sphere. Accordingly, these studies have a quantitative research design and aim to test – through statistical methods – the relations between digitalization, usually considered the independent variable, and selected dimensions of interest, generally measured as dependent variables. As for digitalization, the measurement is mostly related to all dimensions of the DESI, while it is less frequently limited to specific dimensions or selected sub-indicators, that are chosen according to their relevance to the research objectives, e.g., progress in the deployment and use of ICT [Fernández-Portillo, Almodóvar-González and Hernández-Mogollón 2020] or the ownership of electronic devices [Moreno-Llamas, García-Mayor and De la Cruz-Sánchez 2020]. As for dependent variables, some authors provide new knowledge on the relation between digitalization and sustainability [Imran et al. 2022; Martinez et al. 2022; Noja et al. 2022; Esses, Csete and Németh 2021; Jovanović, Dlačić, and Okanović, 2018]. For example, Imran et al. [2022] relied on the five DESI dimensions related to the period 2018-2021 to investigate their direct impact on the sustainable development goals index (SDGI) in all EU countries. A similar analysis was carried out by Jovanović, Dlačić, and Okanović [2020] for all EU countries who found that countries with higher levels of digitalization tend to perform better in achieving sustainability goals in the components of the economy, society and the environment.