stock market index history

What are the biggest percentage drops the stock market (S & P) has seen?

I am very interested in investing the assets of my mother a leveraged index fund. However, I realize that if the S & P were to fall by 50% in one day, all my mother's wallet is gone! What was the largest one-day percentage drop in the history of our stock market? "I can be relatively sure that this fall could not happen? Thank you for your help. The fund would be working with 2X leverage would be an S & P 500 funds.

The largest single day percentage decline in the S & P 500 10/19/1987 Whent that the index fell by 20.4% from 282.76 to 225.06. This day is called Black Monday. Can we be sure that does not happen again? No, there is always the possibility of some important event of terrorism or financial turmoil. Edit: Typo in date due.

Stock Market History S&P 500 Index Technical Analysis Update Pt 1

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