In their study of global connectivity, Facebook identified four main barriers which continue to keep the ITU’s ambitious plan out of reach, and highlights the ways we can overcome these challenges. As the report points out: “These barriers do not arise in isolation, nor can they be addressed in isolation. They function as a cluster, each one affecting the others.”
https://www.weforum.org/agenda/2016/02/4-reasons-4-billion-people-are-still-offline