I had in mind the ^RUA, which only started to break out from the previous top after 5 years, nominally, so you're right, not a decade, but not good for someone trying to retire within that time frame (which doesn't seem like you were).
Still, I worked for a fund that swing traded futures for better returns and less risk than holding the market during this period…
Jesus! What was this average person invested in? From the bottom of the market to back to the prior peak was 3 years for me. And I was so heavy in equities I lost 1/3 of my portfolio's value.
Where does this "decade" come from? The DJIA is nearly 90% higher than the peak pre-2008.
And I know you said inflation, but that has been 1-2% per year since then.