Maybe some of your usual advertisers have experienced changes that have caused them to change or re-allocate their budgets (like if they got dumped in the SERPs, and decided to put more money into the Search Network to make up for it, and take some out of Display)

I had a pretty low day on Friday, but all the other days have been pretty good; including today (and it's not noon yet)

i have seen the same result for sites losing traffic after the new update, it seemed that the well clicked traffic disappeared and has been replaced by some low quality traffic... really weird..

I saw a similar situation to what you described after one of last year's Panda updates. Although your total traffic levels are the same, I would expect that it is indeed different somehow. Possibly more ad blind, possibly less likely to stay on your site for more than a few seconds, possibly even a very different demographic.

Have the referring keywords/sources of your traffic changed significantly? If so, then that would be an indicator that you're now getting a different set of visitors.

Either your CTR is down OR, CPC [AdSense term] is down OR both which is it?

in my case its the CTR; CPC is fairly stable which elminates the possiblity Advertiser of fluctuation.

Perhaps this is a factor?

New matching behavior for phrase and exact match keywords
[adwords.blogspot.com...]

No, because match types really only apply to the ads in search. They keywords for display are there only to give Google some feel for what your site is about. There's no phrase or exact match for the Display Network, because it's not based on a keyword search by the user.

Google's adwords interface now includes a "Display Network" tab that allows advertisers to quickly (relative to before) add new display campaigns.

Perhaps Adwords advertisers are experimenting with display now that it is easier to run, while taking a piece of their text cpc budget away.

The Display Network is what used to be called the Content Network; it includes text ads and image and video ads that run on websites. The Search Network ads run on Google pages and Search partners.

I had added several new adsense units and the drop coincides with that. After days of digging around it appears the new units dragged the entire account down somehow.

Ive picked up this thread after noticing an RPM drop recently also - Im trying to find a historical log of the revenue share Google keeps and it's proving very hard to find.

Has anyone come across an up to date log of this rev share?.

Currently I can see 68% disclosed in my account (which is standard I believe) however from old financial reports I can see it has been up to 78% in 2006

I don't think everyone necessarily gets the same rev share (for example, premium publishers? other partners? domain feeds? no idea) so getting one percentage that covers everything probably wouldn't do you much good. I don't think they even break it down in their quarterly reports.

I'm happy with my cut. Click on your account settings in your adsense control panel. You should see what your percentage of revenue you receive. I remember looking ages ago and the percentage for me is higher now than a few years ago.

Some interesting reading...

Falling online ad rates are good for someone, and it's not Google

Google Inc.'s search-advertising prices plunged 12 percent in the first quarter from a year earlier.

One of the factors that depressed Google's cost-per-click prices is the growth of mobile search: ads designed for mobile devices such as smartphones and tablets.

Mobile-search ads are currently much cheaper than their conventional counterparts, with the average cost-per-click of a smartphone ad running 53 cents in March vs. 60 cents for a tablet ad and 76 cents for an ad that runs on a traditional computer, according to San Francisco-based Marin Software Inc. Those prices are counterintuitive considering that smartphone users were 72 percent more likely to click an ad than a desktop user in 2011.

[chicagobusiness.com...]

Interesting that they say mobile ads are cheaper; my EPC for mobile is pretty darn high (although the CTR is even worse than regular traffic)

I use adsense as well as Tribal Fusion, Burstmedia, Valueclick and Casalemedia all of them have gone down since the first of the year.
These are CPMS (not rpms)
-----------Nov-11 Apr-12

burst ----- $0.63 $0.56
casale ---- $0.44 $0.33
adsense -- $0.70 $0.63
tribal ----- $0.82 $0.61
valueclick - $0.75 $0.62

Either your CTR is down OR, CPC [AdSense term] is down OR both which is it?

Without giving specifics: The number of ads requested increased as you'd expect from adding another website and creating new units, as did the total number of clicks. CPC dropped as did ad request CTR ratio and, ultimately, RPM is down a good deal resulting in earnings nearly cut in half.

So, number of clicks increased but the number of ads requested increased more which apparently sent epc into a tailspin. To me this reaffirms that you need to parse lower paying units from your overall account in order to maintain a higher payout for everything else. It's somewhat counter-intuitive that more clicks would lead to less revenue but that's exactly what happened and it all started at the exact same time I included this site into my account.

Solution(if there is one) is to remove the units from this site and recycle them through my other sites to wipe their memory so to speak. I wish I could just delete them but that's not an option.

Additional information: The number of clicks from 'web cache and other' has quadrupled since adding the last site. I do employ the whitelist in adsense and so I have earned nothing from the new surge in web cache hits but I shudder to think what might have happened to my EPC if I did not whitelist. All of this has me thinking a competitor can indeed cause your overall RPM to drop if they include your adsense code on some spammy sites.

I'll report again if there is any change, for better or worse.

"Either your CTR is down OR, CPC [AdSense term] is down OR both which is it?"

I just noticed that was my 1,000th post since Aug 23, 2003.

I'm gunna go and have another wine on that, 16:18 LT.

Bill, Martini going to join me? Netmeg and Sally can join in just to keep us civilised.

Civilised?

Heh, you don't know me at *all* ork ork

(congratulations)

Come on everyone. Google has share holders to please, so they have to keep hitting their projected income levels. Considering 97% of their money comes from online ads, guess whose money they're taking to make sure they meet their goal?

Got proof of that allegation anywhere?

AdSense for Content revenue share is 68%, just as it has always been.

AdSense for content publishers...earn a 68% revenue share worldwide... Since launching AdSense for content in 2003, this revenue share has never changed. [adsense.blogspot.ca ]

The current revenue share is stated your account settings.

Considering 97% of their money comes from online ads, guess whose money they're taking to make sure they meet their goal?

Most of their money comes from the ads on their search pages. They'd probably save money (and headaches) if they just did away with the content network...

The current revenue share is stated your account settings.

They state that, but it's not like they share the data so I can prove their claim is correct. I just have to take their word for it.

Got proof of that allegation anywhere?

The fact that Google won't let me prove otherwise. If Google wanted to take more, they could, and no one would be the wiser.

Meh. That's true of a lot of things. You are, of course, entitled to your opinion, but that doesn't make it fact.

"Has AdSense Revenue Share Changed?"

No, it has not.

I advertise on adsense and the cpc rates I pay automatically drop if the ad is popular. (upwards of 1% click thrus)

I have my max set at $0.50 but usually pay less than a third of that.

I'm sure thats what happens when I show adssense ads on my sites too which would explain why the "hot" ads dont pay well for long.

Update: a day after making the changes I detailed above the account has returned to normal and EPC is back to what it was before the downturn. Perhaps the most telling graphs I have are the ones for 'previous 30 days' with earnings and pageviews checked. They both sharply intersect and not for the better. Since last night they have switched back.

I could easily test the theory that your payouts are partly determined using account wide metrics by adding the units back to the games site but it has cost me a nice chunk of change already. Coincidence? The timing is too exact imo. Not only that but it happened to all sites in the same manner.

What else could it have been?