Does Google change their algorithms to artificially promote new pages?
Hard to say but there is evidence that QDF exists.

What is QDF?
Google calls the Query Deserves Freshness (QDF).
The QDF basically looks at the current search volume and then the blog post volume to determine if a subject is considered to be hot. If hot, then Google may promote new content to the top of the results. But if this is from June 2007, why are we first really seeing this now? BlogStorm said because there was “no previous search history” for that query and that is why we now see tons of new results.
So 2007 is over, SEO in 2007 changed dramatically. Best practices shifted on a monthly basis, and time-honored methods became obsolete and dangerous – literally overnight. Here are a few of the big changes that made webmasters think in terms of online website organic marketing.
Reciprocal links. In May of 2007, Realtors who relied heavily on reciprocal links started to sob as -30 penalties were dished out by Google, harming their business. It became clear that the decade-old tradition of reciprocal links programs was over. Done. Finished. Time to get one way links.
Looking for tips on a more usable website below is a list of 12 to consider:
1. On the home page make it clear what the site is all about.
2. Make the purpose of each page obvious.
3. User hierarchical headings to give clear structure to the copy.
4. Make the navigation and links obvious.
5. Use clear unambiguous wording.
6. Make the options and next steps obvious.
7. Remove any wording or imagery that is unnecessary, confusing or distracting.
8. Use consistent conventions throughout.
9. Include site search and a site map.
10. Make information such as contact details, pricing and delivery charges clearly accessible.
11. Make the pages printable by including a cascading style sheet for printing.
12. Don’t allow careless errors to make your site look unprofessional.
Descriptions are often overlooked by webmasters, take a look at your pages and see if you can make any amendments to increase the page power on the search engines.
Here at Customer Street we are looking at all our trade specific directories to see if we can see improve our content on our pages and make the Meta data more specific to the pages they are attached. Watch this space for an update.