According to @DowdEdward, seven AI-linked stocks are holding up the major US equity indices and are on their last legs, signaling elevated concentration risk that could undermine index stability if leadership falters, source: @DowdEdward on X, Nov 6, 2025. For trading, high concentration means a reversal in a narrow AI cohort can hit cap-weighted benchmarks harder than equal-weight versions, making breadth and cap-weight versus equal-weight spreads key signals to monitor, source: S&P Dow Jones Indices research on S&P 500 concentration and equal-weight methodology, 2024. A risk-off swing in equities could spill into crypto as Bitcoin has shown rising co-movement with stocks since 2020, increasing downside beta for BTC and major altcoins during equity drawdowns, source: IMF blog Crypto Prices Move More in Sync with Stocks by Tobias Adrian and Tara Iyer with Mahvash Qureshi, 2022.