|Is the Penguin effect page-specific or domain-wide?|
I'm trying to get consensus on what should be a simple question: Are Penguin penalty/effects seen for specific pages, or for entire domains.
For example, if you have a 100 page site, with 50 pages built with dodgy links 25 pages built with clean links, and the other 25 pages not linked, but along for the ride due to domain authority, and Penguin ran, would you expect to see an impact on 50 pages (dodgy links), 75 pages (dodgy + unlinked) or 100 pages (all pages take a hit)?
From what I've seen, it's the entire domain. In my two cases, the links with over-optimized anchor text were pointed to the homepage. Pages don't appear where they should. In queries it doesn't even rank after completely unrelated results.
It's almost like a barrier that deliberately prevents content from the site from appearing in results.
Another symptom ...New content does not rank as it should. For example, on one site a 2000 word post was published today and is indexed, but the tweet announcing it, a feed reader, a google+ post, and 2-3 snippet scrapers all outrank it for very non-competitive terms. In fact, its not even in the Top 100.
From what I have read and seen it is site wide.
I've looked at around 60 sites affected by Penguin, and there are a quite a few where Penguin only struck particular areas of the site, e.g. main site might be affected, but blog completely untouched. Other cases would be internal pages with very strong links which improved in ranking while the rest of the site tanked.
I think the cases where things have been site-wide probably also observe a very high proportion of bad links to the domain root.
Of course as with most things in search YMMV.