Some people don't like to read while some nerds do. Let's acknowledge that there are at least two types of nerd readers. Set #1 have a taste for variety and suffer from slight attention deficient disorder and want to be exposed to a tidbit of information on a very large number of subjects. We can call this group the Wikipedia Nerds (WN). With the advent of the Internet blog, how many WN have substituted from reading books to just reading free blogs? This same group may prefer their information to be "fresh" and not stale. Given the delay in book publishing, blog entries are much "newer news". Set #2 are "deep readers" who want to really dig into a subset of subjects. It strikes me that the percentages of each type here may be 80% Set #1 and 20% Set #2.
While researchers continue to investigate whether free Internet music downloads increase or decrease music sales, a similar question can be asked concerning cross-elasticities. Has the introduction of free access to blogs lowered the demand for costly books? Books have a price to purchase, you have to wait for it to show up, it takes up space in your home or office and it delves too deeply into a single topic.
An empiricist would want to collect some time diaries before and after the introduction of blogs and would want to see how heterogeneous people respond to this "treatment".
Why do I care about this? As a blog writer and a book author, I hope that people are reading both. I worry that the publishing industry may be upended by this trend. Are academic books and popular books written by academics selling fewer copies now than they did before blogging began? Or do blogs increase demand for these books by accelerating buzz and info about them?
Books and blogs: complements or substitutes? It strikes me that for the Set #1 they are substitutes and for set #2 they are complements but given that there are many more Wikipedia Nerds on net they are substitutes.