Hey Heimir,
I'm still in the early stages of using Adsense, but I have heard many stories like yours where the PPC earnings go up and down. But in most cases they will return back to "normal". The ads are being bid on all the time so the prices fluctuate.
How long has this been going on? For how many days have the earnings been lower than before?

You've been smart priced it seems.
Search Google for "smart pricing"

Most of the time it happens when your adsense ads are unrelated leading to clicks but no real conversions for the advertisers. If it continues for a long time Google discounts your CPC.

^ this was going to be my next point.
Can anyone confirm that smartpricing goes on with Adsense?
Maybe with some details behind it on how it's done, etc.

The first step is in analyzing your website.

Perhaps there are some that display unrelated ads. You might want to check that out. I have also heard stories of entertainment/celebrity related websites which tend to get your account smart priced because the clicks are mostly accidental.

Its Google, so no one can say with certainty when you will get UN-smartpriced(cool word eh..

Also, if you have placed ads on site that does not perform at all, remove those ads for now and see if your earnings will go up. I read somewhere that big G does check overal sites performance to determine your earning per click.

How are your traffic? has your traffic been dropped or is it only the earnings

Google has it's own set of standards and parameters while paying to publishers. It is really very difficult to get a perfect answer from Google regarding its payment structure to Bloggers or web publishers. I have searched but not found any successful reply. Thanks

[DELETED]

Refer to this blog post
How To Get Worthless Adsense Clicks | Court's Internet Marketing School - How To Make Money Online

Read the part about "reversing smart pricing" and implement it. All those websites that have a lower than normal CTR.. remove adsense from them and see if you get improvements in your CPC.
The websites that have unrelated ads are more likely to have low CTR's because users aren't interested in those ads. Start by removing adsense from them.

dude, try to filter the ads, i did it for my sites.........for one of my site, i received 15 clicks at one time, but the earning is only $0.25!!! So i try to spot those irrelevant ads especially from directory site, and filter it out......like....

701Panduan - Malaysia Online Directory, Search Maps & City Guide
www.mobissimo.com
Mudah.my - The marketplace of Malaysia
and etc...

Simon

Let me explain why the low CTR contributes to Smart pricing.

It is more of an indirect thing rather than a direct cause of smart pricing. When you have a low CTR it indicates that your ads are not interesting for your visitors. It is very likely that those websites getting unrelated ads are the ones getting a low CTR.

Filtering out your ads won't do much since there is a chance that some of your niche sites simply do not have that many advertisers. Go to Spyfu.com and see how many there are. If there are less than five it is possible that Google doesn't have enough related ads to show.

This is of course a very basic approach.. but it works most of the time. There are many other variables obviously (like a low CTR can be caused by incorrect ad placement).. but as Courtney explained in her post.. it worked for her.

We can only guess at the end... Google doesn't give us conversion statistics of its advertisers.

Depending on your websites.. Id remove adsense from those that have a low CTR and/or unrelated ads and see if it improves my CPC over a week or two.

Spyfu only shows the number of ads running for the search engine results, not the content network.

But yeah, I see where you are going with the relevance between low CTR and irrelevant ads.

I have a very similar situation...Earnings from my niche sites are dropping... and from my other sites that have adsense for content... The traffic is still almost the same but the CTR is dropping...I am not having any problem with adsense for domains though.. only in content..

They'll go back up, it's just the way adsense is. It really depends on your niche to, some are really low than others.

Earning with adsense is really tricky and no one knows how can you earn good and fast with it because google change their policies without intimation and blocked many accounts without any intimation which is really bad sign for such a big company.

It's also not uncommon in tight niches for the primary advertisers to pull out of the contextual ad network.

IS your site seasonal? If so, there might not be sufficient advertisers for this period?
Looks like your site has beensmart-priced. If this is the case, take a look at yoru content and see how relevant the ads are. If they are irrelavent, then use competitive ad filter and block these out. You can use CAF regardless to filter out the low paying advertisers. I did this and myearnings went up within a few days.

I woudl also try and build backlinks to your site from relavent sites, e.g. write a few articles for EZA that are related to yoru product niche and try to also use other web2.0 sites such as squiddo and hubpages and get some backlinks, this may help.

Some days you will notice a decrease in earning and sometimes an increase, if its consistenly on the low try the above. Hope it all works out and its only a temporary thing.

Good luck
Zaheer

it's a well known fact that adsense earnings drop over a period of time.It happened to my sites and i've heard many webmasters say the same thing.
You could also check out other publisher networks like the yahoo one

Well known fact? How long until they start to drop for everyone? Is it like months or years or what? Mine has just gone up, not in a straight line, but if you improve your skills, then your earnings improve. I haven't noticed any kind of vast conspiracy.