Drawing a Fibonacci retrace from the low of Black Monday 1987 to the highs of Summer '07, the crash retraced down to the .618 fib or a 54% loss.
Drawing a Fib from the the Feb 2009 low to the Feb 2020 high, the .618 fib line would be around $15,000 and the last '07 high of $14000 would be support.
This would correlate with a similar crash of 50+% if the market fails to rebound back above the 50 Week Moving Average line (in red) and breaks the 200 Week Moving Average (in blue).
Interest rates were 10% in 1987. They are 1.7% in 2020. The environment is different. The stock market leans on a dovish Fed to prop it up now. I think this will ultimately keep dips short lived and markets inflated