My adsense earnings usually vary a fair bit from month to month - not wildly so but, for example, from February to April last year earnings in the best month were one and a half times the worst. This makes sense because there is a seasonal element to both the amount of traffic and the sources of traffic.
Over the last three months my earnings have been the same to with 0.5%, and it looks like this month is heading the same way.
Any ideas about whether I should be worried?