In the comments to a previous post in which I deride those who keep on telling us SF is dying, Jetse de Vries notes from the bestseller list of 2008:
…basically *one* SF novel in the top 100 (and it barely scraped in), and 5 in total in the top 150. Two of those by very well-established authors (Stephenson and Card), three of those media tie-ins. Fantasy? Already starting with Stephenie Meyer at number 3... Make no mistake: fantasy is selling better than SF, *much* better. Look at the 2010 catalogs of genre publishers, from Tor to Pyr: all predominantly fantasy titles.
I have one little problem with this and with others, like Mark Charan, who make a comparison between fantasy and science fiction sales, or cite science fiction’s proportion of the market, as proof that science fiction is in decline, dying, whatever. Why do they assume it’s a zero sum game? Why do they make the illogical leap that because fantasy is selling well science fiction must be doing badly? Do people assume that because sales of teen vampire books are on the increase, thriller sales are decreasing?
I guess what you really need to do is get data on year on year sales of SF back over six decades and plot trends. You’ll probably find all sorts of lulls and highs, so would have to be careful about making assumptions upon seeing a present upward or downward trend. Possibly science fiction sales have never been as good as they were in the Golden Age, but are they worse than they were 20 or 30 years ago? Maybe someone could put together a computer model to check all this out, in fact, I know just the guys who could do this, and give you whatever answer you wanted.