Bond Shock Tops Fund Managers' Worry List in September
A messy spike in bond yields was the No. 1 tail risk in the September 2026 BofA Global Fund Manager Survey, according to Bloomberg. A tail risk is a rare shock that can cause wide losses. A bond yield is the interest rate on government debt, and it helps set mortgage rates and the value investors place on future profits. Cash holdings rose to 3.9% in that September survey, according to Yahoo Finance.
In August, a disorderly rise in yields was the second-biggest fear, named by 27% as their top worry, according to Trustnet. Equity exposure stayed high. Managers held 56% of portfolios in stocks in the survey reported Aug. 20, according to Bloomberg.
In July, investors turned the most bullish since February, according to Bank of America's survey. In that July survey, 45% named AI bubble risks as the largest tail risk, as reported July 14 by Reuters. Late 2025 was focused on AI valuations and spending. On Nov. 18, 2025, an AI bubble was the biggest tail risk for 45%, according to Reuters. That report noted a record share said firms are "overinvesting". In a survey reported Oct. 14, 2025, a record share said AI stocks are in a bubble.
The broader context here is a shift in the left tail. For much of the past year the main worry was concentration in AI stocks and the spending behind them. In September the main worry was the discount rate, the rate used to value future earnings. Stock hedges help with the first worry. Cash and shorter bond exposure help with the second.
In my view, the two September numbers belong together. Cash at 3.9% with bond-shock fear on top points to worry about speed and spillover. A fast rise in yields tightens credit, lowers the extra return for holding stocks, and hits long-term bonds and fast-growing stocks at once. Cash buffers soften that blow.
Looking at what this means for positioning, July to September tells a clear story. July paired peak bullishness with 45% citing AI bubble risk. August kept stocks at 56% while bond-shock fear was second at 27%. September lifted bond-shock fear to first while cash edged up. Managers kept stock exposure even as faith in steady yields slipped. That leaves portfolios exposed to jumpy bond pricing and heavy government borrowing. The problem is not higher yields alone. It is a disorderly move.
