During a recent Search Marketing conference, Matt Cutts (Google’s head of search spam) announced that the infamous Panda update is going to be rolled out in monthly installments/updates. The algorithm is going to be updated and ammended each month, with the live effects of the update taking place throughout the month.
The repeated cycle of updates will take place once each month, with the effects taking place slowly over that month. So for example, if Google update the algorithm on the 1st of each month, the results will slowly change throughout the month based on the initial update.
Back in March, Google stated that they would stop announcing major Panda updates as the ammendments were more suitable to be made as rolling updates. In this sense, the rolling updates cycle will usually go over a period of 10 days or so.
Without the warning of an impending Panda update, this announcement now means that SEOs and Webmasters need to be on top of their content in terms of quality, keyword density and overall quality.