“…The explaining theoretical approaches show variety as well. Most frequently, zero-price effects (Hüttel et al, 2018;Niemand et al, 2015;Papies, Eggers, & Wlömert, 2011), the ladder of participation (a concept of increasing activity in a social network ranging from passive to active contribution, (Bründl, 2018;Oestreicher-Singer & Zalmanson, 2012), prospect theory (Koch & Benlian, 2017;Rietveld, 2018), and the theory of planned behavior and its variants (Lin, Hsu, & Chen, 2013;Papies et al, 2011;Schreiner & Hess, 2015) are used.…”