To be fair, physical book sales were down in 2009, when this was written.
Though I wonder how relevant such a statistic is in the context of this discussion. Is there really a difference between me reading some long-form piece online (like this one) - in terms of, for example, the concentration requirement (which this piece seems to care deeply about) - and reading it in a newspaper (other than probably fewer typos)? The same could be said for reading a novel I found on https://www.gutenberg.org compared to reading the equivalent physical book. Except that reading it online is free, and at least equally (possibly more) accessible.