@CaptainGrumpy, I saw your comment on shorting BHP today so thought I would update my BHP chart I posted on 9th Dec 2015. It's playing out in a fairly predictable way, although with a lot of weekly volatility.
In my initial post I discussed that once price falls through its ATH50% level, in this case $22.65, it carries on down with momentum and then will reverse back up to about ATH50%, before finally falling to the ATH25% level.
The inital level of fall is not quite predictable. I thought it would get support at the $17.30 line and turn back up around that. It paused there, but then extended the fall to the next support at $14 before it then it turned up. This is point 3 on the charts.
We are on our way back up to ATH$22.65, which looks like hitting in May but could still stay up there for June and July. This is point 4 in the charts.
Have a look at what happened in 2006 on the way up through the $22.65 level as highlighted in purple shading. It punched through the level by 29%, spent 8 months coming back to the level and slightly below it, then went on to All Time highs. Same thing in reverse.
Initial Chart from 9th Dec 2016
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Current Chart.
View attachment 173522