My site had been getting high CPC for the past few months, however it is starting to drop again. I notice that CPC is still high in the morning, then it starts to slow down by early afternoon. By the evening it is practically nothing, so the high CPC I has at 10am drops by nearly 40% by midnight. Any ideas why CPC would drop so low as days goes on? Traffic is the same as it has been for months.
I guess it would depend on what ads are being shown to your visitors. Because of Google's Interest Based Ads, it would be nearly impossible to figure out what ads each person sees. If they see low-paying ads, then that's what you're going to get paid.
Besides the type of ads being served could be changing, where your traffic is coming from also will impact the price your getting per click. For example if the majority of your traffic in the morning is from the United States your click prices are going to be higher then if they are coming from China.