For years, PPC managers have been advised to use seasonality adjustments to prepare for major retail events like Black Friday and Cyber Monday (BFCM). The conventional wisdom suggests these adjustments help Smart Bidding systems anticipate increased conversion rates and bid more aggressively. However, a new three-year study by Optmyzr challenges this long-held belief, revealing that for highly predictable events like BFCM, these adjustments often inflate costs and significantly reduce Return on Ad Spend (ROAS).
Fred Vallaeys and the Optmyzr team analyzed performance across three BFCM cycles from 2022 to 2024, examining up to 6,000 advertisers annually. The core question was simple: do these adjustments genuinely help during Black Friday and Cyber Monday, or do they merely prompt Google to bid higher without meaningful gain? Based on their extensive data, seasonality adjustments frequently hurt efficiency and rarely deliver the breakthrough many advertisers expect.
Key Findings from Optmyzr’s BFCM Seasonality Study
The study compared performance across three BFCM periods (2022–2024), defined as the Wednesday before Black Friday through the Wednesday after Cyber Monday. Each year’s results were measured against a pre-BFCM baseline. Accounts were grouped into two cohorts:
- Advertisers who did not use seasonality bid adjustments
- Advertisers who did apply them
Across all three years, consistent patterns emerged from their research.
#1: Smart Bidding Already Adjusts for BFCM Without Manual Prompts
A crucial finding was that Google's Smart Bidding systems inherently adapt to the surge in conversion rates during BFCM, even without manual intervention. For advertisers who skipped seasonality adjustments, Smart Bidding still responded to the conversion rate spike:
- 2022: Conversion rate up 17.5%
- 2023: Conversion rate up 11.9%
- 2024: Conversion rate up 7.5%
In other words, the algorithm did exactly what it was designed to do. It detected higher user intent and increased bids accordingly, rendering external nudges unnecessary for predictable events.
#2: Seasonality Adjustments Inflated CPCs Far More Than Necessary
The study further revealed that seasonality adjustments led to disproportionately high Cost Per Click (CPC) inflation. Optmyzr notes that:
When you apply a seasonality adjustment, you are effectively telling Google: ‘I expect conversion rate to increase by X%. Raise bids immediately by X%’.
Smart Bidding tends to take this prediction literally, usually without softening or testing it. The study showed this is why CPCs climbed much faster for advertisers who used adjustments:
CPC inflation (no adjustment vs. with adjustment)
- 2022: +17% vs. +36.7%
- 2023: +16% vs. +32%
- 2024: +17% vs. +34%
These adjustments consistently doubled CPC inflation, despite Smart Bidding already increasing bids based on real-time conversion signals.
#3: ROAS Dropped for Advertisers Using Seasonality Adjustments
The most significant impact was on Return on Ad Spend (ROAS). When CPC increases outpace conversion rate improvements, ROAS inevitably suffers.
ROAS change (no adjustment vs. with adjustment)
- 2022: -2% vs. -17%
- 2023: -1.5% vs. -10%
- 2024: +5.7% vs. -15.7%
While the "no adjustment" group maintained stable ROAS, even showing improvement in 2024, the "with adjustment" group experienced steep declines every year, highlighting a clear efficiency trade-off.
Why Do Seasonality Adjustments Struggle During BFCM?
Optmyzr attributes this dynamic to a precision issue. Applying a seasonality adjustment involves making a specific prediction about conversion lift. If this estimate, for example, +40%, overshoots the actual lift of +32–35%, the discrepancy directly translates into overbidding.
As Fred Vallaeys writes:
Smart Bidding takes this literally. It does not hedge your bet. It assumes you have perfect foresight.
This literal interpretation is the core problem. Furthermore, Black Friday and Cyber Monday are highly predictable retail events. Google possesses years of historical BFCM data, allowing its models to accurately anticipate expected shifts. As a result, Optmyzr concludes:
Seasonality adjustments work best when Google cannot anticipate the spike.
BFCM clearly falls outside this category, being practically encoded into Google's bidding models.
The Trade-Off: More Revenue, Lower Efficiency
Despite the efficiency concerns, the study did show that advertisers using seasonality adjustments often achieved higher revenue growth:
Revenue growth (no adjustment vs. with adjustment)
- 2022: +25% vs. +50.5%
- 2023: +30.3% vs. +52.8%
- 2024: +33.8% vs. 39.9%
In 2022 and 2023, the incremental revenue jump was significant, but these gains were consistently accompanied by notable ROAS declines. This leads to a practical interpretation:
- If your brand’s priority is aggressive market share capture, top-line revenue, or inventory liquidation, seasonality adjustments can deliver greater volume.
- However, if your brand’s priority is profitable performance, these adjustments tend to work against that objective during BFCM.
When Seasonality Adjustments Do Make Sense
Optmyzr emphasizes that seasonality adjustments themselves are not flawed; rather, their misuse is the issue. They prove effective in scenarios where advertisers genuinely possess more insight into a spike than the platforms do, such as:
- A short flash sale
- A new, one-time promotion without historical precedent
- A large, concentrated email marketing push
- Niche events with limited global relevance
Conversely, situations where they may not be optimal include:
- Black Friday and Cyber Monday (as supported by the study)
- Christmas shopping windows
- Valentine’s Day for gift categories
These events are already extensively modeled by Google's bidding systems, making manual adjustments redundant or counterproductive.
What Should PPC Managers Do With This Data?
For PPC managers preparing for the upcoming holiday season, Optmyzr's findings offer actionable insights.
#1: Default to Not Using Seasonality Adjustments for BFCM
For most advertisers, allowing Smart Bidding to naturally manage the conversion rate spike during BFCM leads to more stable ROAS and fewer unwelcome surprises. The study's consistent data across three years strongly supports this approach.
#2: If Leadership Insists on Volume, Be Explicit About the Trade-Off
Leverage Optmyzr's findings to set clear expectations with stakeholders, moving beyond mere opinion to data-backed insights. For instance:
-
Optmyzr’s three-year analysis shows that seasonality adjustments can increase revenue but typically reduce ROAS by 10-17 percentage points.
-
We can use them if revenue volume is the priority, but we must prepare for significantly lower cost efficiency.
These examples frame the discussion around business objectives rather than just tactical decisions.
#3: Spend Your Energy on Guardrails, Not the Predictions
Optmyzr reminds advertisers that trusting the algorithm doesn't mean relinquishing all oversight. Instead of attempting to predict exact uplifts, a PPC manager's value during peak season comes from implementing robust guardrails:
- Smart budget pacing
- Hourly monitoring (ideally with automated alerts)
- Strategic bid caps when necessary
- Audience and device segmentation checks
- Ensuring creative and offer readiness
These areas represent crucial points where human judgment and proactive management surpass algorithmic predictions.
Final Thoughts On Optmyzr’s Study
Optmyzr's study does not condemn seasonality bid adjustments entirely; rather, it underscores that context is everything. For predictable, high-volume retail events like BFCM, Google's bidding systems already possess the necessary signals. Introducing a manual forecast often results in overshooting, inflated CPCs, and avoidable efficiency losses.
However, for unique or brand-specific spikes, these adjustments remain a valuable tool.
This research provides PPC managers with a rare commodity during the BFCM rush: solid, data-driven evidence to support a more measured, less reactive approach. It offers the confidence and backing needed the next time the question arises: "Should we turn on seasonality adjustments this Black Friday?" Your answer can now be confident, data-driven, and unequivocally clear.
