As the S&P 500 trades at new highs, historical data suggest the coming week could be brutal for the benchmark index.On Friday, the S&P 500 closed at 6,664, up about 0.5% for the day, extending a rally of more than 4% over the past month.S&P 500 one-month price chart. Source: Google Finance Looking ahead, two decades of data on the SPDR S&P 500 ETF Trust (SPY) show that the upcoming week has often produced negative results, according to insights from charting platform TrendSpider.Seasonality patterns point t ...