Many Amazon sellers have recently experienced a puzzling phenomenon: advertising budgets remain unchanged, bidding strategies stay consistent, yet Return on Ad Spend (ROAS) for Sponsored Brands (SB) and Sponsored Display (SD) campaigns has plummeted by 50% or more. Before questioning your operational capabilities, consider that this likely stems from Amazon's updated ad attribution rules.
The Truth Behind ROAS Decline: Amazon's "Shopping Signal Boost" Attribution Model
Previously, Amazon's display attribution worked simplistically: any order placed within 14 days of a user seeing your ad (even peripherally) would credit that advertisement. This inflated performance metrics, often misleading sellers into believing their ads were more effective than reality.
Effective January 2026, Amazon introduced its "Shopping Signal Boost" attribution model. This sophisticated system analyzes genuine purchase intent signals including:
- Whether products were already in shopping carts before ad exposure
- Ad placement visibility and engagement quality
- Post-impression search behavior for related keywords
The fundamental distinction between old and new models:
- Legacy Model: Ad impression → Purchase → Automatic credit
- New Model: Ad impression → Intent analysis → Credit only for genuinely influenced conversions
Most Affected Advertising Types
The update disproportionately impacts certain campaign formats:
- Sponsored Brands: Particularly broad-match and auto-targeting campaigns
- Sponsored Display: vCPM-based placements vulnerable to "empty impression" deductions
- Amazon DSP: All display-focused campaigns within Amazon's demand-side platform
Notably unaffected formats include:
- Sponsored Products (click-attribution remains unchanged)
- CPC-based SD campaigns (focusing on post-click conversions)
Three Strategic Adjustments for Sellers
Rather than reactive bid adjustments, implement these data-driven approaches:
1. Recalibrate Performance Benchmarks
Compare 7-14 day performance across attribution models. A drop from ROAS 5.0 to 3.0 indicates 3.0 now represents true campaign effectiveness. Recalculate break-even points accordingly.
2. Optimize Budget Allocation
Eliminate underperforming campaigns that previously benefited from inflated attribution. Redirect budgets toward campaigns demonstrating genuine incremental sales.
3. Leverage Full-Funnel Metrics
Analyze the delta between "All Views" and attributed conversions. Large gaps indicate over-reliance on existing customers. Shift focus toward new customer acquisition through refined audience targeting.
Additional Consideration: Aged Inventory Fees
Concurrently, sellers should address Amazon's aged inventory assessments:
- Complete removal of overage stock by January 15
- Monthly fees update on the 15th - removal requests must be submitted by 11:59 PM on the 14th
This attribution update ultimately benefits sellers by eliminating vanity metrics. While short-term ROAS declines may appear concerning, the transparency enables more strategic budget allocation toward genuinely productive advertising efforts.