My google adsense earning is getting smaller and smaller

Anyone notice beginning of year 2013, google adsense earning has been getting smaller and smaller, less click, click with lesser earnings than ever? Am I the only one or everyone feel this impact? I have doing the same thing I’ve been doing, update blog entries and as frequent as possible on multiple websites. COuld it be google adsense or search engine optimization getting smarter it can detect low quality contents websites or so call micro blog?

I have not done any research yet on google in regards to this lower earning from google adsense, look like I will be spending some time try to find out what’s going on. Could be my websites, could my web server, could be google adsense paying less now, and a lot of other possibilities.