Viral coefficient vs. industry/company


Has anyone ever seen a list of typical viral coefficients by industry or company.

For example, Zappos has a fantastic brand, so a bunch of their traffic must be from indirect sources (referrals or direct visits) vs. advertising.

Another way of asking the question is if there is a source (by industry/company) of portions of sales that come from direct ads (a link on Google, Facebook, affiliates) vs. non-direct (e.g., brands or referrals)?

I am trying to get a sense of how much various companies or industries depend on direct ads vs. leveraging the value of their brands.