Hard Disk Sizes, Over Time...

I came across the graph at right while reading the Wikipedia article on hard disk drives (I'm a geek, what can I say).  Like many other aspects of computer technology, hard disk drives keep increasing in capability (in their case, capacity and to a lesser extent performance) and decreasing in price.  The declining price curve ($ per megabyte) I've long been familiar with, but this chart of capacity over time was fascinating (click to enlarge).

In rough terms, it looks like for the past thirty years, average disk capacities have increased quite steadily by about 60% per year.  This is quite close to the same factor by which the $ per megabyte declines, and jibes well with an observation many people have made: the price per disk drive is relatively invariant.  I'm not sure if that's just coincidence, or if it reflects market forces driving the capacity inversely to the $ per megabyte...