At the time of posting this question, the BlackRock ETF XSP is down approximately 1.3% during the period Dec 24 9:30 am - Dec 31 10:30 am, while the actual index is down approximately 0.3% during the same period. BlackRock's ETF IVV, which comprises 98.3% of XSP, and which also tracks the S&P 500, is also only down approximately 0.3% during the same period. Why is this happening now, all of a sudden? Throughout the year XSP tracks the actual index very closely. Thanks.