They have received increased political interest at EU level, with the development of transnational programmes in macro-regions as well as macro-regional strategies, thus far for two areas that share a common water basin.15'16 Two cross-border initiatives in the United States (with Canada and Mexico) resemble macro-regions given their scale. Many such networks, with various degrees of depth and stability, exist. First, such configurations are more likely to focus on innovation-driven economic development opportunities than broader geostrategic or infrastructure considerations. Second, with geographic proximity, the economic exchanges and flows of people, capital and knowledge may be more intense within such cross-border regions than in the other types.