it took 37 days to go from 600 to 500
it took 75 days to go from 500 to 400
it took 38 days to go from 400 to 300
lets assume that the price at lower values means the oscillation of 75 will be twice as long ie 150 days
150 days since january 2 is about 1 june.
so I am calling 1 June as the date we leave $200
that means of course we also break $100 about 7 august 2015
breaks every rule of maths/analysis but if you are felling nervous this will put you in a real spin.
if you are sensibly holding while all this rides out then you can also sensibly disregard this post and leave it to the weak to run the price for a while