Maybe because I'm working at present on a figure whose critical stock was once high but has fallen dramatically, I'd like to see someone (not me) put together a line graph called the "Literary Stock Market." Although you can get a sense of this if you read the year-end reviews in various discplines, it'd be nice to see this in graphics form, wouldn't it?
Although numbers of conference, conference panels, and so on could help to determine rankings, you could also get a pretty good ranking by basing the Literary Stock Market on the numbers of citations in the MLA Bibliography each year, for a start. Whoever puts together the Literary Stock Market could also have little line indicators giving possible reasons if there are drastic rises and falls. For example, if you were working on James Fenimore Cooper (I'm making this up), there could be a spike and decline around the topics of American exceptionalism and the whole "American Adam" idea, maybe followed by a revival after postcolonial theory arrives. It would be hugely interesting as well to see how authors neglected in previous centuries have been revived or recovered.
You could also do this with individual books, as the classic, must-read novel of one generation of critics recedes before an interest in another of the author's books. You'd probably want to limit this to a particular area or time period, too, since following more than 15 or so lines would make the viewer dizzy.
I think you could do this in history: topics or figures once considered essential for study may have fallen into obscurity, and previously neglected topics may come to the fore.
Are there any figures in your discipline whose stock on the Literary Stock Market has fallen particularly far, or whose star has risen drastically?
[Edited to add: Speaking of popularity, that's why Joel Stein is against net neutrality. Shorter Joel Stein in this week's Time magazine: "Some sites should receive priority, including Fox News, if they are more important to many people, and especially to me, Joel Stein. How dare independent sites get in the way of my Glenn Beck, Lady GaGa, and Lindsay Lohan news? Fie upon the masses yearning for unpopular information not sponsored by a corporation! Let them eat cake--or at least wait longer while I get vital updates paid for by corporate America!" The article is so ridiculous that I think, or maybe hope, that he's kidding.]