Por This report has been produced with best updated information and statistics in June 2020. The nature of the issues addressed involves a number of assumptions and results in estimations. Unless it is explicitly mentioned, all methods and sources for this paper are available at The Size, Socio-Economic Composition and Fiscal Implications of the Irregular Immigration in Spain, working paper from Ismael Gálvez-Iniesta (Carlos III University of Madrid), which can be accessed here.
Foreign, essential and undocumented: A snapshot of irregular immigration in Spain (2020)