According to @StockMKTNewz, on October 19, 1987, the S&P 500 fell 20.5% and the Dow Jones dropped 22.6% in a single session, marking the worst day in U.S. stock market history known as Black Monday (source: @StockMKTNewz). In response, U.S. regulators implemented market-wide circuit breakers that now pause trading at S&P 500 declines of 7%, 13%, and 20% to curb disorderly moves (source: NYSE; SEC). For crypto traders, major equity selloffs have been associated with higher BTC–equity correlations, making these trigger levels useful risk markers, while CME Bitcoin futures also employ price limits and velocity logic that can pause trading during extreme moves (source: IMF; CME Group).

According to Evan (@StockMKTNewz) on Twitter, April 4, 2025 marked the second largest daily point loss in S&P 500 history, signaling heightened volatility and risk-off sentiment in global markets (source: Twitter, May 25, 2025). Such dramatic stock market declines often trigger increased crypto trading volumes as investors seek alternative assets and hedges. Traders should monitor Bitcoin and Ethereum price action for potential surges in volatility and liquidity, as major equity sell-offs historically correlate with short-term crypto market turbulence.

According to The Kobeissi Letter, the S&P 500 dropped nearly 80 points within 30 minutes at 1:00 PM ET due to a weak 20-year US Treasury bond auction, which caused Treasury yields to spike sharply (Source: @KobeissiLetter, May 21, 2025). Elevated yields often trigger risk-off sentiment, leading to equity sell-offs and increased volatility across financial markets. For crypto traders, the rapid shift in US yields can signal tightening liquidity and potential downside for major digital assets, as institutional investors may rotate capital out of risk assets like Bitcoin and Ethereum into safer government bonds. Monitoring US Treasury auctions and yield movements remains critical for anticipating crypto price swings and managing trading risk.