We focus all of our attention on optimizing our sites, but sometimes it is not our sites performance that results in missing our Adsense earnings goals. If you are looking at December results and thinking that you didn’t quite earn as much as you expected, don’t rush to change anything that you hadn’t already identified as broken.
Many advertisers have budgets that run out before the month of December ends. Furthermore, those budgets are often not renewed until a few days into January. To compound this type of thing, two other market activities kick in that can decrease your earnings. Many advertisers simply stop spending ad money from about the 25th through about January 2nd. If they have nothing to sell to holiday consumers, their money might get more bang for its buck when people that they are targeting come back online AFTER the holidays.
Plus, many companies and advertisers that do have consumers to target can move into the vacancies mentioned above and pay far less in Adsense money to run their own advertisements. The supply of ads shrink and the bargain hunters move in. Its classic economics, and it can account for decreases in Adsense earnings during December.