“…The majority of the em-pirical PWYW studies, which analyze external RP, support these suppositions (Armstrong Soule and Madrigal, 2015;Gautier and Van der Klaauw, 2012 (in case of incidental customer encounters with PWYW offers); Jang and Chu, 2012; (in case of hypothetical payments); Kim et al, 2014a;Krawczyk et al, 2015;Lee et al, 2011Lee et al, , 2015León et al, 2012;Parvinen et al, 2013;Perfecto et al, 2013;Perfecto et al, 2014;Pöyry and Parvinen, 2014;Pöyry et al, 2013;Regner and Barria, 2009;Riener, 2008). Furthermore, several PWYW studies, in which customers were provided with information on the variable production costs of the goods offered, find significantly positive correlations between the level of the stated direct costs -which can be regarded as a special variant of external RP -and the level of voluntary customer payments (Jang and Chu, 2012;Kim et al, 2014a;Krämer et al, 2015;Schmidt et al, 2015; for an insightful theoretical analysis of this association see Greiff et al, 2014). In light of these results, it is not surprising that earlier reviews of the empirical PWYW literature summarize the state of the evidence as follows: "the provision of external reference prices in the form of a regular or suggested price usually has a positive impact on the prices paid [voluntarily]" (Stegemann, 2014, p. 33; for similar summaries see Gahler, 2016, p. 31;Pöyry, 2015, p. L-28).…”