After a few days, Sitrix took a meter reading in order to identify the sites most affected by the update of Google’s algorithm. The SISTRIX Visibility Index is calculated from the traffic generated on keywords, their ranking and the click rates of the different positions on the results page.
So according to Johannes Beus, from Sistrix, who analyzes Jason Calacanis’s site, Mahalo, as an example. The latter would not only have seen the number of keywords on which it was referenced, go from 33875 to 9799, but for the two thirds of the remaining words, Mahalo only goes back from the 8th page of results!
Here is the list of the 25 sites that suffered the heaviest losses. It should be remembered that this update has not yet been rolled out apart from the US version of Google.