A question about dance of death

No. They only choose to stock albums they believe will 'stay' in the top 20 for a while. It saves updating the wall every week.
 
Its on the wall and in the listning station in HMV pitt st. I know thats not what you were asking but its pretty cool !
 
By deciding what to stock and what not too, they influence the top 20 as much as anything else. Therefore, the top 20 is generally whatever they want it to be.