How much traffic?

It hit me too. My earnings dropped 60% in two days.

Yes, my earnings also have dropped, don't know whether it is because of holidays here.

CTR (clickthrough rate) is more an indication of the quality of ads being served on your website. A higher CTR generally means better targeting, that your ads are more relevant to your visitor's interests. Advertisers come and go. The ads created by these advertisers come and go with them. If your CTR falls, it is by no means an indication of any penalty or smart pricing. It simply means fewer people are clicking on the ads being served on your sites. As for why fewer people are clicking, the usual culprit is different ads. New ads coming in - old ads going out. This has been my experience anyway.

And of course it depends on your traffic quantity.
Lots of traffic and you will be able to compare by the hour.
Little traffic and you can only see "real" trends over weeks or months.

It seems logical to me that if Google decides your site is low quality, they may forward crappy ads to you which no one will click anyway so it may be a form of smart pricing.

I guess it's possible there could be an account-wide targeting effect of some kind, but by definition this is not smart pricing.

If you're confident the numbers you're talking about are statistically significant, take a look at the ads showing. If a change in ad targeting has really dropped CTR by a factor as massive as 80%, the ads should be markedly different.

[Just noticed you're saying ads are the same. I'm going to fall back on the numbers probably not being statistically significant; possibly related to the fact that you posted very early into the new reporting day.]

It hit me too. My earnings dropped 60% in two days.

I suggest you don't draw conclusions based on a few days.... My best month ever included two of my worst days ever... Adsense =/= rocket science.

I suggest you don't draw conclusions based on a few days.... My best month ever included two of my worst days ever... Adsense =/= rocket science.

The last three months have been the best so far. I'm just a bit worried about this drop.

Genuine1,
My traffic is relatively low in comparison to most sites I see here, but it was two different sites that had the same problem. That is what bothered me

Codegal

Wyweb, I think that may have been the case when you talk about the quality of ads. But why at the same time. Why on both websites?

Hmm maybe it is some sort of audit

I think google started doing the same thing as the adwords quality score does for landing pages with adsense.

If your page quality or site quality seems low then as GreenGrass said earlier they may send you lower click through rate or lower paying ads.

During this same period I and some others seem to have had a small increase in both!

But natural statistical variations mean you cannot see any meaningful trends daily unless you normally get a good few hundred clicks per day anyway. And even then, its still subject to the usual external effects of advertising budgets, the auction system, hols, events, seasonal stuff, TV, new links appearing or vanishing, search quality / quantity as updation occurs on different engines etc.