According to the Jane Austen Society of North America (JASNA), "In 2008, a prime opportunity arose for taking a more systematic look at this interesting community of Austen readers. The theme for the annual meeting of JASNA was to be 'Austen’s Legacy: Life, Love, & Laughter.' Believing that Jane’s greatest legacy is her devoted readership," a detailed survey of their membership was conducted. The Anatomy of a Janeite are the results.
And so on. Go to the full survey results here.
An aside: Here's a humorous look at what a typical Janeite would look from the point of view of Austen's various books.
[Edited 5/28/14: It has come to my attention that the image below is copyrighted by Sandra Florance and is available for purchase as a 5x7 notecard at the Etsy store Turtle Doves.]
[Click to see a more readable image.]