Why does RPC change every day in search arbitrage?
RPC is set by a live auction, so it moves whenever advertisers change bids or budgets. It also shifts with the day of the week, the season, the visitor's country and device, and the quality score the search engine assigns to your traffic. Feed-wide policy or pricing changes can move it sharply overnight with no warning.
Normal causes include advertiser budgets running out late in the month, weekend dips in business-focused verticals, and seasonality such as the Q4 effect. These are predictable and can be handled with dayparting and bid adjustments.
Less visible causes sit on the feed side. Smart pricing reduces what advertisers pay for clicks from sources that convert poorly, so a decline in your own traffic quality shows up as lower RPC. Coverage and ad depth can fall, meaning fewer ads are shown per search. And the engine can change terms across all partners at once: System1 said a network-wide Google change in June 2026 cut its RSOC monetisation by more than 30%.