Forum Moderators: open
For example, a sub-page could have more incoming links than the index page.
Of course, in the real world, most webmasters link to and ask for links to their index page more than to particular sub pages. This leads to a tendancy for the index page on most sites to rank highest, then the other pages to rank in terms of their link-distance from the index page.
On the other hand, a significant minority prefers to promote their more specific (and hence usually deeper on the site) pages at the expense of a more generic index page. On those sites, the sub-pages will tend to out-rank the index page.
Jim
Dave