Updated: November 18, 2016 12:22 PM [ET] | Originally published: November 18, 2016 12:18 PM EST; During the 1990s, two amateur historians, Neil Howe and the late William Strauss, developed a new theory of American history in two books, Generations: the History of America’s Future (1991), and The Fourth Turning: An American Prophecy (1997). They identified an 80-year cycle in American history, punc