Is it just me or do earnings seem to drop towards the end of the month? The CTR is the same but the CPM drops dramatically around this time of the month for my website. Is is because their Adwords accounts run out of money or something towards the end of the month?
AdWords campaigns have daily budgets, actually, though it's certainly possible that advertisers may stop ad campaigns manually if they've reached a certain amount of spending for the month. Looking at my earnings, they're all over the map at the end of the month, sometimes higher than the average for the rest of the month, sometimes lower.
Correct me if I'm wrong with regards to AdWords, I thought there was a daily budget that tries to stick to a target, but isn't fixed. As in if your monthly advertising budget is $3100 and you allocate $100 a day, users may click beyond $100 though it'll shut off soon after so you CAN go over your daily budget allocation. However, Google ensures that you DON'T go over your monthly allocation... so if you spent the $3100 before the month is out, your ads don't show and you don't have to pay an extra dime. So that could be a reason for dwindling end of month phenomenom.
It's true, you can set monthly budgets if you use the optional Budget Optimizer tool. Don't know how many advertisers do that, to be honest. If you don't, you're limited to a daily budget.
But advertisers having thier ads stopped shouldn't affect EPC and CPM for content Adwords unlike search.