Linkedin has 200 million members and there are more than 3 billion people in the workforce globally. Even excluding industry/education/location-specific workers, that’s still a lot of people who are not on Linkedin, so make other platforms/stratagems work for you in the search for connections. Use trade newsletters, association membership lists, Facebook and Google to locate those relationships that have been ‘left behind’. Send a marketing letter to introduce yourself/nurture known/unknown contacts and good-paper-snail-mail congratulations to people who have achieved something worthy. Be different, be special and make others special as well.