Hi Dr Mike,
Looking at Richards chart the overall range for the day was 75 points on each.
But in column K we have a 43 point rise in the futures and a 57 point rise in the cash.
No, the overall moves were the same. On the futures there was a brief retracement that can be seen in column L of the futures before it continues up in column M to the same height as the D4F move. The total size of this retracement was 11 points (from 3583 down to 3572). At the same time the D4F quote went from 3623 down to 3614, 9 points but not quite enough to give a 3 box reversal. Note that if the D4F quote had been a single point higher at the time the retracement started then the 9 point move would have resulted in a 3 box reversal!
So at most, you could claim that there was a 2 point bias introduced here. More likely there was a slight spike up in the futures before the retracement and a slight spike down at the bottom of it. Remember that the futures chart is formed from actual trade prices whilst the D4F one is from the mid point of the spread.
Some of which can be accounted for by D4F's habit of switching the spread from under to over the base price as the price moves from a downward trend to an upward one, but not all of it.
This doesn't make any sense as an explanation. If this had happened then the retracement would have been present - and larger - in the D4F chart. More generally, if this was the case then why aren't the major moves larger on the D4F chart than on the futures one?
I strongly suspect all that you are refering to here is the simple fact that the futures lead the cash and the D4F 'cash' quote is based on the futures. The futures regularly move a few points further than the cash index and move slightly in advance of it.