What portion of adult people worldwide have a smartphone?
According to https://www.bankmycell.com/blog/how-many-phones-are-in-the-world, as of 2023 an estimated 86.29% of the worldwide population own a smartphone. If we assume that the proportion of children with smartphones is the same as that of adults with smartphones, then we could also guess that roughly 86% of adults worldwide have a smartphone. However, we could speculate that this 86% is an underestimate, since it's feasible for a lower proportion of children to have smartphones due to parental controls, and hence more adults would make up the portion of overall smartphone users.