عوامل تعیین کننده استفاده از سایتهای شبکه های اجتماعی از طرف دارندگان مدرک دکترا: تجزیه و تحلیل بر اساس LinkedIn  Determinants of PhD holders’ use of social networking sites: An analysis based on LinkedIn

1. Introduction Today, the routine practices of everyday life have incorporated Internet services and social networking sites (SNSs). Among other aspects, the spread of the Internet has had a great impact on professional lives. This is due to the pivotal role of information in labor markets (Autor, 2001) and in the development of professional networks. In particular, the Internet may have important implications for the careers of highly skilled individuals (Acemoglu, 1998; Cairncross, 2001; Varian, 2010). Not surprisingly, the use of the Internet is significantly more widespread among highly skilled workers than among low-skilled ones. However, little research has been conducted on how highly skilled individuals use Internet applications and, in particular, SNSs. Some studies provide evidence on the effect of the diffusion of broadband infrastructure on employment at an aggregated level (see for instance Czernich, 2014). Other evidence suggests that Internet-based technologies are effectively adopted in order to establish collaborations and networks at greater geographical dis- ∗ Corresponding author. E-mail addresses: stefano.baruffaldi@epfl.ch (S.H. Baruffaldi), giorgio.dimaio@mail.polimi.it (G. Di Maio), paolo.landoni@polito.it (P. Landoni). tances among universities and firms (Ding et al., 2010; Forman and van Zeebroeck, 2012; Hoekman et al., 2010). Few authors have investigated the use of specific Internet platforms. As noted by Zide et al., “most of the empirical research on SNSs [. . .] has focused on Facebook”, a non-professional site, even when studying recruitment processes (Zide et al., 2014). Finally, in academia, some studies have demonstrated that a large number of researchers increasingly make strategic use of Internet-based tools (emails, personal web pages, SNSs) to coordinate team activities, promote their competences and professional profiles, disseminate scientific results and establish new connections (Bar-Ilan et al., 2012; Barjak, 2006a; Barjak et al., 2007; Mas-Bleda and Aguillo, 2013; Walsh et al., 2000; Ward et al., 2015; Winkler et al., 2010). In this work, we contribute to knowledge on this topic by analyzing the use of LinkedIn’s SNS by PhD holders graduated from two European institutions: the Politecnico of Milan in Italy, and the École Polytechnique Fédérale de Lausanne in Switzerland. We focus on PhD holders, given their high level of qualification, and their importance in the creation and transfer of knowledge (Casey, 2009; Stephan, 2012). PhD holders play an important role in the innovation process, in pure and applied research, and especially in the transfer and diffusion of knowledge (Herrera et al., 2010; Zellner, 2003) and its economic exploitation (Agrawal, 2006; Herrera and Nieto, 2015). The number of students awarded a doc torate each year has increased greatly worldwide in recent years (Bloch et al., 2015), and the job searching strategies of younger generations are changing nature thanks to the Internet-based technologies (Smith, 2015). Consequently, understanding how SNSs are adopted by PhD holders, and how they influence their professional trajectories, has implications for the debate on the modes of creation and transfer of knowledge. Furthermore, insights on the dynamics of this emerging digital environment can help policymakers to develop adequate policy responses.