I'm working in a SEO research company. We are making researches regarding to changing in websites position. Here are few interesting facts we found: 1. Websites with a lot of content are crawled more often. The position of that websites is changing frequently. 2. Google recognize websites which are edited frequently and crawl them more often. Position is changing accordingly. 3.The most interesting fact: Traffic alone increase website crawling rate. We found that small websites with a lot of traffic which haven't been edited, change theirs position frequently. You can make your own keywords position research with our company research tool: www.exactfactor.com