About this CPC

I do google around how to increase CPC.
Do what it claim etc

but my CPC is low suddenly or can't get high

is it quality of traffic?

I do place the ad in the " Standard " position which many successful adsense users place
just that CPC suddenly low or even go high not say very high

or due to my niches?

 

The CPC is determined by the advertiser .... its what they are prepared to pay.