“…The simplest is a nominal variable based on the presence or absence of similar firms. This measure was used almost exclusively in early newspaper competition studies (Bigman, 1948;Borstel, 1956;Duncan, 1952;Grotta, 1971;Kearl, 1958;Nixon & Jones, 1956;Weaver & Mullins, 1975;Willoughby, 1955) and has been used for more recent studies as well (Busterna, Hansen, & Ward, 1991;Candussi & Winter, 1988;Entman, 1985;McCombs, 1987McCombs, , 1988. This measure assumes that any two firms in the same geographic market producing similar products would be acceptable substitutes for buyers.…”