Once you’ve started taking apart the search engines, you’ll need to keep on top of when there are swings in the algo and one of the easiest ways to do this is to monitor your niches yourself.
Personally I use WebCeo to do this.
Setup competitor tracking against your own project URL and get all the competitors on the top 2 pages for the keywords you want to rank on. The easiest way to do this is to setup a project for each keyword you are running checks against with each project containing all the competitors for the given keyword. Then just run daily reports and you’ll see just how much flux there is in the results. You need to periodically revisit the results to see if there are any other competitors that have popped in there, but you can then start to examine why these results have appeared and drill down.
Some of the biggest universes of search do some big sector changes, but the differences between the finance niche and the home cooking niche is a whole lot of money, so it's good to keep your eyes on where you clients are.