GoogleAlgorithmUnconfirmed
Dewey
Large but never-explained spring 2008 reshuffle of results, reported by the industry as a broad ranking change.
What changed
At the end of March 2008 the industry recorded a substantial reshuffle of results across many query classes, nicknamed Dewey after a Google engineer's forum post. Google acknowledged that something had changed but never described the mechanism or published guidance. It is included here as a well-documented but unconfirmed volatility event.
Not confirmed by the engine. This entry documents a change that was widely observed and reported, but never officially acknowledged. Treat the dates as approximate and the mechanism as inferred.
Timing
Rollout began 31 March 2008. No completion date was announced. Rankings typically remain unstable for the whole rollout window, so measurements taken inside it are not a reliable read on the outcome.