The S&P 500 index, as tracked by the SPDR S&P 500 ETF Trust (NYSE:SPY), has shown resilience with daily fluctuations never exceeding a 1.5% drop for more than 100 trading sessions. However, as the calendar moves to the last days of September, the index is entering what Bank of America calls 'the worst 10 days of the year' for the S&P 500 in terms of seasonality. Technical analysts at Bank of America predict the corrective trend of the index to extend further.