There is a cyclical pattern to historical change. Most institutional change occurs in periods the book calls "Crisis Eras", whjich occur once every 80 years. The last Crisis Era was the Great Depression and WW2. Before that was the Civil War. And before that was the American Revolution. In between each Crisis Era there is an "Awakening Era" of rapid cultural change. The period from 1964 to 1984 was the last Awakening Era.