No, I don't think nice round numbers like 20 or 100 years show a pattern. I like to think more in terms of generations: 15 to 30 years. I can't predict the future. Please take my 30 year time-line idea as numerology where similarly numbered years must resemble each other. It's broken into a decade each of boom-bust-war:

  1890 boom "Klondike Gold Rush"
  1900 bust "Panic of 1901"
  1910 war WW1
  1920 boom "Roaring"
  1930 bust "Great Depression"
  1940 war WW2
  1950 boom "Golden Age" [1]
  1960 bust [2]
  1970 war Viet Nam
  1980 boom "Long" [3]
  1990 bust [4] [5]
  2000 war Afghanistan, Iraq
  2010 boom [6]
  2020 bust [7]
  2030 war [8]

Of course, there are booms, busts and wars occurring at anytime. And some parts of the world might feel like they are in the future and some in the past.

[1] https://en.wikipedia.org/wiki/Post%E2%80%93World_War_II_econ... [2] https://en.wikipedia.org/wiki/Recession_of_1960%E2%80%931961 [3] https://www.hoover.org/research/ten-causes-reagan-boom-1982-... [4] https://en.wikipedia.org/wiki/Early_1990s_recession_in_the_U... [5] https://en.wikipedia.org/wiki/Dot-com_bubble [6] https://www.forbes.com/sites/chuckjones/2020/02/17/obamas-20... [7] https://en.wikipedia.org/wiki/Economic_impact_of_the_COVID-1... [8] https://www.rand.org/content/dam/rand/pubs/research_reports/...