“…2 Previous empirical research on network effects in the labor market is based either on survey information on the use of informal search methods, such as friends and relatives, or on administrative records in which networks are defined indirectly using observable proxies, such as neighborhood, firm, or ethnicity. Studies on the use of informal search methods include Simon and Warner (1992), Pistaferri (1999), Marmaros and Sacerdote (2002), Loury (2006), Bentolila et al (2010) and Pellizzari (2010). 3 Studies defining networks indirectly using proxies include Topa (2001), Weinberg et al (2004), Bayer et al (2008), Hellerstein et al (2011) and Schmutte (2015), who use geographic proximity at the neighborhood level; Cingano and Rosolia (2012), who define networks at the firm level; Edin et al (2003), Munshi (2003) and Beaman (2012), who define networks based on immigrants' ethnic origin; and Dustmann et al (2011), who use information on both firms and ethnicity.…”