It could be even simpler than that -- maybe there's a really popular job board that's attracting all the customers? MySpace losing hundreds of thousands of users didn't mean there were less teenagers.
A 40% decline in real tech-hiring rates would be a shocking, sudden decline. The simpler, most consistent, and most likely explanation is that the author's data isn't representative of the big picture.
It's very similar to "my helloworld.c won't compile, the compiler must be broken"
Edit: if the author has only been in the business a couple of years, he may not be aware of the historical boom/bust nature of it - yet.