This was the move in S&P 500 futures in December (for the November release):
One month may be a blip but two months of such price action, and there's certainly something amiss with the report surely. The White House downplayed the potential for a leak last month but if we do see something similar today, suspicions will certainly grow over the integrity of the data.
We're less than an hour away now, so just be mindful of any such moves in the run up to the data in case. This is the biggest report on the economic calendar in markets in this timeline, so it will not be short of volatility whatsoever.
