The period under examination is roughly from 1900 to 1960+. In the Rwave ( top ) the square waves are approximately World War I and World War II. The second wave is a first approximation of capturing some of the waves of migration. The first increase in Amplitude is from the rural South to the urban North. The second increase in amplitude is the larger migration from the rural South to the urban North.
Below is the Bwave that tries to make visible the Zeitgeist as we move through the 20th century.
Any thoughts or suggestions are much appreciated.