When using long tail search phrases for products (items to purchase), google generally returns multiple URLS for various ecommerce sites, but it hides additional urls for each site behind
.
Each site tends to get one URL in the SERP and the rest are hidden (this isn't always the case as sometimes it shows 4 or 5 pages for a given domain but they are almost always grouped together).
Since the related pages for each domain show up grouped together in the original SERP, is google using domain authority to determine ranking for the collection of pages, or is it ranking the entire set of pages for the domain based on the one page it chose to display in the SERP?