Many of my pages ranking in Google exhibit this strange behavior where they would be ranking for a week or two on page 1, then drop for a week or two to page 2 or even below (sometimes not found at all) , then rank again back on page 1. This has been going on for months now, for about a year I would say, since Summer 2012.
One thing I noticed is that all these "flickering" pages have rating shown on the page and marked up as structural data (http://schema.org/aggregaterating). The more popular the page, the more chances are that someone votes on its content. Up or down, does not matter. What seems to matter is that both the ratingvalue and the ratingcount values change by one digit with each consecutive vote.
Usually, it is almost a guarantee that if you change the page's content, its Google ranking will suffer until the page is re-crawled and re-indexed and its new content is re-evaluated. So, if the new vote was looked at in terms of HTML change, it would be so insignificant compared to the pages' 25K+ content size that I don't think the ranking would change in any way. But what if the change in structural data is looked at differently? I mean, if the page only has two or three votes, an additional vote can change the value by significant 20%+
So, do you guys think this structural data markup change plays a role in the ranking changes or can the continued rank flickering be explained by something less esoteric?