Today, I spent some time trying to find out information about who your typical astrology column reader is. A couple of hours worth. And I still don't know.
While I have found some information, it is all third party information.
Interestingly enourgh, the articles and sites that do cite demographic information are all anti-astrology: astronomy, Christian (anti-magic and anti-divination), and fraud awareness sites. The professional astrologers seem to have made their own typical customer a trade secret.