The goal of the project is to detect algorithm changes and or sweeping penalties that affect SEOs and their clients.
If you're an SEO and you see SERPs rankings plummet, the first thought that crosses you mind is "what did I do?". This tool may verify that you're not alone... or then again maybe you are!
It's like walking into a big room filled with a few hundred SEOs and saying "Hey, did anyone notice anything weird with Google today?" (this happens in SEO forums a lot) But in this case you get back real data and pretty graphs instead of subjective opinions.
Positive changes are good, negative changes are bad. The graph does not compound the data from day to day, it simply shows each day's overall change from a baseline of zero. A day of +7 and then a day of +4. like we recently saw, is unusual and would mean that our customers saw an average increase of 13 positions on their keyphrases over those two days.