adsense cpc down this year

last november my adsense was fully restricted, after about a month it was restored. The revenue and CPC took about a week to return to previous levels. But then starting this year 1st jan the CPC took like a 50% nose dive.

Has their been some kind of algorithm change to cause this CPC decrease, as my sites more or less the same, in fact now its actually faster aswell.

Has anyone else noticed their cpc go down start of this year?

Yes this is completely normal. All big company spent their whole marketing budget in the last quarter of the year. Iam running ads and the cpc and cpm just got 50% cheaper.