A casual look at the graph above leaves me thinking that the x axis for the main graph is the one with the years marked out on it. I think this happens for several reasons:
- The actual x axis doesn't pop out at me (it has more marks and less contrast)
- There's not enough vertical separation between the two graphs - I think even having a thin line of separation would help.
- The year-scale graph at the bottom is so faint it's hard for me to see that it's there.
- The year labels on the x axis for the year-scale graph are above the graph, instead of below it.
This is a beta (but hasn't that term suffered a meaning decay?), so they're actively making changes. They've done some interesting things to it recently in which they annotate the graph with news stories that were released at the associated point in time. They've also got a handy management view where you can quickly find out about the recent stock activity of the executives.