Resumen: This paper investigates the factors that influence the national distribution of city sizes, using data from both gridded population estimates and nighttime lights. Leveraging a global definition of human settlements, it also accounts for spatial units smaller than traditional urban centers. To address model uncertainty in identifying robust determinants of cross-country variation in urban concentration, the analysis employs Bayesian model averaging techniques. Across different samples, openness to trade, the Polity score, and natural resource dependence consistently show posterior inclusion probabilities of approximately 50 % or higher. The findings highlight the potential roles of international trade and institutional quality in fostering more balanced national urban systems. Idioma: Inglés DOI: 10.1016/j.cities.2025.106184 Año: 2025 Publicado en: Cities 166 (2025), 106184 [14 pp.] ISSN: 0264-2751 Tipo y forma: Artículo (Versión definitiva) Área (Departamento): Área Fund. Análisis Económico (Dpto. Análisis Económico)