Quote from increasenow:
does not make sense...you could also say..."if the ES is up, the ES is up overnight"...does not make sense as the ES tracks the SPX
You may have misunderstood the OP's comments since what you express is not congruent with the OP's assertion.
I believe what he said was....... holding overnight makes money 78% of the time, IF you buy at the cash close.
His statement can be verified by induction. Induction is not a good test however because induction is not a good idea for modelling. The induction reveals that RTH periods are net negative and non RTH periods are net positive.
The OP is talking about the non RTH periods which are net positive. He is long oriented as indicated by his word "buy".
Were he to have hypothesized that selling short at the close and seeing that it was a losing proposition, he would have proved the null hypothesis for the case he advocates.
By doing this, he eliminates black swans from his original hypothesis.
Saying things about winning or losing has to involve complete statements about the testing; we all know that.
You will find in the future, perhaps, how the cash and futures indexes relate. At this point, you have not availed yourself to the many strategies that show SS profitable results by using these two in various relationships. Try not to draw conclusions that exclude you from delving into some very profitable situations.
It is noteworthy that there is reason why RTH margin is different from non RTH margin.