The advice that I will give you is first do your research before applying for residency, gather all relevant documentation, ensure that all documents are either apostilled or authenticated and legalized and translated into Spanish; if you plan to do the application yourself and cannot speak Spanish...
The most pronounced interest in studying intraregional and interregional differences in population income manifests itself in large countries (China [1,2,3], the USA [6,8], Canada [9]) or a group of countries (the European Union [15]). For these purposes, most scientists use the Theil ...