Advertising efficiency peaked in late 2025 but recently turned negative. Q4 2025 Shopping conversions surged roughly 35 percent while costs remained flat. By Q2 2026 efficiency deteriorated sharply as Search conversions plummeted around 25 percent despite slight cost increases. Mobile continues to heavily dominate both spend and conversions across all campaign types.
The 365-day trajectory reveals severe margin compression during the Q4 holiday peak. Costs spiked significantly sharper than conversions, indicating aggressive CPC inflation driven by intense seasonal competition. Post-holiday efficiency continued to degrade; costs remained sticky through Q1 and Q2 while conversions steadily declined below pre-peak baselines, signaling a tightening acquisition environment.
Year-over-year data complicates the high-level trend. While overall efficiency appears strained, Standard Shopping is a massive outlier, driving ~30% YoY conversion growth across Q3–Q1 with only marginal cost increases (<5%).
Mobile is the primary efficiency engine for product-based campaigns. For both PMax and Shopping, mobile generates roughly 80% of conversions but consumes only ~65% of the cost. Desktop clicks carry a significant premium, yielding a much higher Cost-Per-Acquisition (CPA).
These fluctuations align with broader algorithmic and macroeconomic shifts: