Inflectional systems vary along multiple dimensions (number of members, size of paradigms, word class, integrative complexity, accidents of history, etc.). This makes it difficult to find significant correlations and causality relations between different properties, as attested systems usually differ in multiple ways at the same time, thus obscuring possible relations between individual variables. Here we analyze the relation between a system’s size by number of members and its morphological complexity. We do so by exploring in detail, via quantitative methods, the cognate inflectional systems of Central Pame and Chichimec (Otomanguean, Mexico), whose inflecting nominal classes differ precisely mostly with regard to their size (i.e. number of members).