It's been 15 days since I upgraded my web host from a VPS to a private server (within the same company). In the day after the upgrade my adsense CTR dropped by half and my CPC increased by about 70%. Nothing was changed on the website.
What could have caused this CTR drop?
[edited by: rlopes at 9:16 pm (utc) on Nov 1, 2012]
if the site's IP address changed then maybe google reset all the site's data. (it sounds a bit wierd... surely they would go by the domain name? but who knows how they work.) so they might not know what the best performing ads are anymore. it will probably work itself out if you give it enough time.
if it was me, i wouldn't go changing anything just yet, in case you unwittingly change something that is actually working okay
I would just assume it's some transient issues that typically seem to take about 2 weeks before everything resumes back to normal after moving anywhere. If it's still a problem after several weeks I'd be more worried.
Also, it's also a bad time at the moment, you did hear that on the West Coast the Giants won the World Series and millions were out celebrating the other day while across the country on the East Coast there are millions still without power and millions more are busy out cleaning up all the flood water, sand and debris everywhere left by Hurricane Sandy. Not to mention the fact that anyone relying on cellular broadband access in those areas are probably not having much luck getting online due to the heavy volume usage at the moment.
Plus lots of people in other parts of the US and other countries have been out celebrating Halloween, taking their kids Trick or Treating, partying and sleeping in with hangovers, etc.
Perhaps that has something to do with it?
TIP: read world events now and then as it will impact your CTR ;)