S&P 500 Rally Fragile as Hope Outpaces Cash Inflows

As of May 20, equity markets led by the S&P 500 are driven more by investor optimism than fresh liquidity or robust inflows, leaving gains vulnerable to setbacks. The seven-week rally began stalling in Asia on May 14 amid rising global yields, then re-accelerated on AI-driven positioning and record dealer gamma exposure that peaked at the highest levels since 2021. HSBC maintained its maximum overweight to equities, citing 27.7 percent blended Q1 earnings growth and the strongest earnings-beat rate since 2021. Warnings from May 17 onward highlighted 30-year Treasury yields reaching 5.12 percent and potential stock-to-bond rotations, culminating in the latest assessment that constrained cash leaves the rally exposed if flows disappoint.