Early this year Google initiated its “Panda” algorithm change which affected the rank of millions of websites. In a February post on “The Official Google Blog” they explained their motivation:
“This update is designed to reduce rankings for low-quality sites—sites which are low-value add for users, copy content from other websites, or sites that are just not very useful. At the same time, it will provide better rankings for high-quality sites—sites with original content and information such as research, in-depth reports, thoughtful analysis and so on...
We can’t make a major improvement without affecting rankings for many sites. It has to be that some sites will go up and some will go down. Google depends on the high-quality content created by wonderful websites around the world, and we do have a responsibility to encourage a healthy web ecosystem. Therefore, it is important for high-quality sites to be rewarded, and that’s exactly what this change does.”
Read the whole post: http://googleblog.blogspot.com/2011/02/finding-more-high-quality-sites-in.html
The “Panda” changes created so much interest that Google offered more advice two months later, on their "Webmaster Central Blog":
“Some publishers have fixated on our prior Panda algorithm change, but Panda was just one of roughly 500 search improvements we expect to roll out to search this year. In fact, since we launched Panda, we've rolled out over a dozen additional tweaks to our ranking algorithms, and some sites have incorrectly assumed that changes in their rankings were related to Panda. Search is a complicated and evolving art and science, so rather than focusing on specific algorithmic tweaks, we encourage you to focus on delivering the best possible experience for users.”
You can read the entire posts from Google on the links I've provided above. But it is not hard to see what Google is looking for. As they see it, their job is to find the best and most relevant content locations, rank them, and present them to their users. Through this process sites with higher quality content will rank higher.
In their their words, websites that create "original content and information such as research, in-depth reports, thoughtful analysis and so on" are bound to come out ahead. This is why many companies are making original content creation part of their search engine optimization program.