On June 10, the trading departments of Barclays and Goldman Sachs issued a warning that last Friday's sell-off caught investors, accustomed to momentum stocks only going up, off guard. However, investors should not easily dismiss it as a one-time anomaly. Factors such as crowded positions, narrow market breadth, and the prospect of interest rates remaining high for an extended period make the US stock market more susceptible to sudden pullbacks. Goldman Sachs trader Lee Coppersmith and others wrote in a report to clients: 'These factors together create an environment where the impact of factor trading unwinding may be far more severe than the volatility levels indicated at the index level.' Alexander Altmann, head of global equity tactical strategy at Barclays, stated that following last Friday's sharp decline, volatility-controlled funds may need to reduce their US stock allocations by about 14 percentage points. This would represent the largest single-day de-risking operation since February 6.