“…advertising, R&D and exports) at varying capability levels. Earlier studies investigated the joint effects of advertising and R&D (Askenazy et al, 2016;Doloreux et al, 2018;Hsiao et al, 2021;Hughes et al, 2018;Kwon et al, 2022b;Peng et al, 2018); R&D and exports (Baldwin et al, 2016;D'Angeloa et al, 2020;Sikharulidze and Kikutadze, 2017); and exports and advertising, or marketing in general (Hultman et al, 2011;Jindal, 2020;Lee and Kwon, 2021;Makrini, 2017;Morales et al, 2019;Zhang and Zhu, 2016). Despite diverse views and differing results in various empirical settings, most of these studies were devoted to testing hypothetical statements, with the effects confined within a linear or curvilinear format, with the rare exception of nonparametric approaches (Kwon et al, 2022b;Lee and Kwon, 2021).…”