Since the Great Depression the S&P 500 tracks U.S. GDP, both log graphed here such that the slope of the channel is the log slope of U.S. GDP.
Looking for some kind of pattern, there might be a ~33 year wave-like pattern repeating twice since 1929 and hypothetically a third time, as depicted.
The likelihood of the third repetition happing I have no confidence for or against, it's just a possible pattern I'm proposing in the data.