The Google search result pages are often very unstable. Whoever is ranking on page 1 today might already be pushed away by competitors tomorrow. This is why it is important to keep an eye on changes and adjust your own actions accordingly.
In SISTRIX you can take a look at the search result pages at two separate points in time and see at a glance which URLs gained a higher position, lost or potentially even entirely disappeared off the ranking. See, what happened on these pages and learn for your own pages.
