Exponential

You don't think progress goes in a straight line, do you?  Do you recognize that it is an ascending, accelerating, maybe even exponential curve?  It takes hell's own time to get started, but when it goes it goes like a bomb.

-- Frederik George Pohl, Jr. (1919 - 2013), award-winning science fiction writer and editor, with a career spanning over seventy-five years, Day Million (p. 441)