Resumen: Using urban data from the last available census of the five BRICS countries we have tested, by means of a rolling sample regressions approach, whether, as Eeckhout (2004) proposed, the Pareto exponent in a standard Zipf equation is decreasing as more cities are added to the sample. The results are very conclusive: Eeckhout's hypothesis is satisfied for Brazil, Russia and South Africa, but for India and China there are non-negligible parts of the distribution where it is not fulfilled. We also test the fulfilment of Zipf's law: it holds in the upper tail of the five countries (except South Africa) but for the rest of the distribution the predominant outcome is rejection. Idioma: Inglés Año: 2021 Publicado en: Economics Bulletin 41, 4 (2021), 2543-2549 ISSN: 1545-2921 Originalmente disponible en: Texto completo de la revista