The birth of the concept of the “global city” suffered from the beginning of a problem of lack of statistical data that really corroborated the hypotheses about the emergence of new nodal spaces of the global economic network located in the cities as new nuclei of economic concentration. It has always been a hypothesis that is difficult to confirm beyond speculation and observation, but it clashes with the difficulty of obtaining reliable and valid data over time for a sufficient number of cities.

Global Urban Analysis. A Survey of Cities in Globalization recaps the research effort of Globalization and World Cities Research Network and the Global Urban Competitineness Project of the Chinese Academy of Social Sciences by parameterize the scope of economic globalization in its urban aspect and thus try to obtain a method of analysis to measure the global component of cities or, better, the urban component of global economic flows. The GaWC network, led by Peter Taylor, one of the leading academics on the relationship between cities and globalization, she has specialized in these issues for years and the alliance with the Chinese academy has allowed her to deepen her analysis and refine a method of analysis and statistical compilation which is the one presented in the book , resulting in a compendium of the application of this method to different regions and cities.
The empirical work is based on the synthesis of the concepts of Saskia Sassen and Manuel Castells to result in a Globalizing Cities Index, an index that tries to relate the functions as centers of power of the cities and their functions as space centers for advanced services of the global economy. This work is completed with an analysis on a regional scale (Europe, North America, Asia-Pacific, Australasia, South Asia, Eurasia, the Middle East and North Africa, Sub-Saharan Africa and Latin America) to define both the relative role of cities of these parts of the world in their own region, as well as the role of each region in relation to others and, especially, to the main centers of geographic power of globalization. The same work is exposed for sub-regional or national spaces, thereby also allowing to explore the behavior at the national level of some cities and others in relation to their role in the globalized economy in comparison with other cities in their immediate environment.
In the case of Spanish cities (included in a joint chapter with Portugal), the work is carried out by Simón Sánchez Moral, researcher at the Department of Regional Geographic Analysis of the Complutense University of Madrid, and manages to review data from Barcelona, ​​Madrid, Lisbon, Seville, Porto, Valencia and Bilbao. It is in the chapters dedicated to this subregional scale where one of the most interesting elements appears, in my opinion, and which could have the longest journey in the research of the coming years because, in addition to reviewing the relative position of cities with respect to their environment , their connectivity is analyzed and compared with respect to the traditional global powers (represented by London and New York) versus the connectivity with the new global economic powers represented methodologically by Beijing, Hong Kong and Shanghai. The results of these tables are a good indicator of where things are going and shed some statistical light on the suspicion of how the economic flows between the urban nodes of the global economy are moving from the old power to the new emerging urban powers. And, at the same time, it is a good guide to find out if a city is managing to connect with these centers or not.

The weakest part of the investigation may apparently be the database on which the analysis is built. Specifically, this study measures the presence in the flows of the global economy of the 525 cities studied based on the worldwide distribution of the offices of 2,000 companies considered from different criteria as the most relevant multinationals in six sectors considered central in the global economy (financial and banking services, advertising agencies, legal services, advisory, insurance and consulting). When selecting data from the composition of the puzzle of the economy of advanced services of the global economy, all the flows of the industrial sector are left out, which despite the tertiarization of the world economy, continue to be basic, I believe, to understand the movements of the economy. I understand that the research is precisely based on a theorization of the global urban system that tries to attend to the most characteristic components of the globalized economy, but leaves out global processes of distribution of manufacturing in the world, processes that are also a consequence of the economic globalization. To this we could also add that there are also limitations in the selection of source data (other tertiary sectors could always be included, a greater number of companies or more varied criteria to select them and, above all, measure the economic dimension of the presence of multinational offices in a city rather than presence itself), but the effort would have great difficulty in finding reliable and comparable data. Possibly, that is where the new evolutions of the methodology will go.