But your reference to repetitive twenty year segments of time and repetitious behaviour patterns for some reason brought back memories of those days in the late 50s and early 60s. (remonline.com)
• Even if equity returns in the future are projected to replicate the worst 50 - year segment in the Standard & Poor's (S&P) 500 history (1929 to 1978), 401 (k) accumulations are still projected to replace significant proportions of projected pre-retirement income. (ebri.org)
The market avg over these cycles is between 0 - 4 % the decade following these cycles averages 17 % hence why they say long term market avg is 9 - 10 % it should be viewed in 30 year segments not 10. (financialsamurai.com)