An ID 200 tics/bar chart is showing a refresh phenomenon indicating too few tics/bar for reliable data.
I have not seen this phenomenon (a chart changing after a refresh) since moving to DTNIQFeed/QT months ago BUT it is clearly evident in the pair of charts below [PM II follows PM].
Until the exact reason for this is determined, one should use ID (intraday) gap data for YM with appropriate caution. The most obvious reason is, as I said, a refresh artifact but if so, it would be peculiar to YM. Highly liquid instruments like SPY don't show this which makes me doubt the refresh explanation (this arises from data lag). What one is left with then, is late trades, over which the trader has no control. There may be other explanations but I am not aware of them.
On the other hand the interday data is as reproducible as one can get, IMO, and thus is very believable (aside from whether or not one perceives gaps to be important). So we are left today with a close below the lower gap margin [actually an outside down day on increased volume], having failed rather miserably on the upside. Note that the gap construction makes NO PREDICTION about which way the market is going but rather points out certain obstacles which could be in the way of it going where it wants to go.
lj