“…First, much is now known about which IPIs exist and about the similarities and differences in their institutional design (Alger and Kille, 2014;Cofelice, 2015Cofelice, , 2018Cutler, 2001;De Puig, 2008;Habegger, 2005;Kissling, 2014;Winzen and Rocabert, 2021). Second, recent studies have given us in-depth knowledge of the reasons why IPIs are created and empowered (Cofelice, 2018;Grigorescu, 2015;Lenz, 2019;Lenz et al, 2019;Rocabert et al, 2019;Schimmelfennig et al, 2020;Verdoes, 2020;Winzen and Rocabert, 2021). Third, there are systematic explanations of why individual members of national parliaments engage with IPIs (Lipps, 2021;Malang, 2019;Wagner, 2013).…”