original_query: What is the significance of Black Monday in relation to the stock market crash in October 1987?
query: What is the significance of Black Monday in relation to the stock market crash of October 1987?
answer: Black Monday (October 19, 1987) refers to the global stock market crash, the largest one-day percentage drop in the history of the Dow Jones Industrial Average (DJIA), falling 22.6%.  It caused worldwide losses estimated at US$1.71 trillion and sparked fears of extended economic instability.