With a few exceptions, the federalism and territorial politics literature overwhelmingly focuses on self-rule, or autonomy, when analysing the territorial distribution of power. However, this neglects a second, equally crucial aspect: shared rule, or regional co-decision making at national/central level. This paper questions the validity of this one-sided perspective, conceptualises different types of shared rule, theorises the causes and consequences of different types of shared rule, and tries to show empirically what difference shared rule can make to the real world. To take this latter step, it relies on the latest edition of the REGIONAL AUTHORITY INDEX dataset (Hooghe et al. 2016) and undertakes a cross-sectional analysis