1:30 Ratio for Information

The post at Librarian.net about the book containing thirty tables-of-contents reminded me of the 1:30 rule for information.
Dolby and Resnikoff found these relationships:

• A book title is 1/30 the length of a table of contents in characters, on average
• A table of contents is 1/30 the length of a back of the book index, on average
• A back of the book index is 1/30 the length of the text of a book, on average
• An abstract is 1/30 the length of the technical paper it represents, on average

Is this the result of living in the material world and this won't hold true online? Or is this a function of the brain and how it deals with information and likely to hold true where ever we function?