For the last three years, my CPC has generally been 30-50 cents (higher between Thanksgiving and Super Bowl) for an iOS and Android game site. After the 2014 super bowl it dropped to 22-25 and has continually slid, now averaging 12-15 cents. Traffic has been about 70-15-15 mobile-tablet-desktop this whole time, FWIW.

Has anyone else had this kind of CPC drop and if so, how have you combatted it? I have considered dropping my ad units from 3 to 2 or even 1 but I'm not sure that would work because my link units don't fare much better than my standard ad units. And for what it's worth, my most highly clicked unit is a 300x1050 that has been active since around September this year, and I'm sure it generates more accidental clicks than the others. Not sure if more accidental clicks would lead to a lower CPC across the board or not. Would switching that one to a more conventional unit help?

Also I have tested various solutions for one day at a time or so (35,000 impressions per day so one day is usually a good barometer) but if one of the above solutions were to change the CPC at all in not sure how long it would take to see a difference. I have been reluctant to go beyond that time span because my CTR is fairly high compared to what it used to be, so my overall RPM is still pretty decent. But increasing CPC would allow me to get rid of some ad real estate and keep a similar income.

And finally, all three of my ad units are responsive units. None of em are standard units.