FORTUNE editor-in-chief Clifton Leaf introduces the magazine's annual list of the World's 50 Greatest Leaders: “If 2018 becomes the year that the United States finally begins to tackle its disease of gun violence ... it will be due not to the good sense of elected officials, but rather to the courage, tenacity, and sheer eloquence of students."

The top five: The students of Marjory Stoneman Douglas and other schools; Bill and Melinda Gates, cofounders, The Gates Foundation; The #MeToo Movement; South Korean President Moon Jae-in; and Ken Frazier, Merck CEO.