The CPC offered in Jan 2013 by Adsense is very low. A google search on the topic sapys that its all time low month. Are you experiencing the same. a suggestions to improve the same would be highly appreciated.
This is normal, mate. Happens every January, but starts to pick up towards the end and by February. don't worry too much. All I would say is analyse your traffic and make sure you're not missing out on mobile users due to adformats (such as the ads are too big for smartphones). During this month, due to the drop in CPC, I looked at optimising Adsense on my site. Ended up increasing earnings from mobile traffic (which was about 50% of visits for some sites). Good luck.