Every Q4, the same message shows up in our accounts:
“Use seasonality adjustments to get ready for Black Friday and Cyber Monday.”
On paper, it sounds reasonable. You expect conversion rates to rise, so you give Smart Bidding a heads up and tell it to bid more aggressively during the peak.
Optmyzr’s latest study puts a pretty big dent in that narrative.
Over three BFCM cycles from 2022 through 2024, Fred Vallaeys and the Optmyzr team analyzed performance for up to 6,000 advertisers per year, split into two cohorts: those who used seasonality bid adjustments and those who did not.
The question was simple: do these adjustments actually help during Black Friday and Cyber Monday, or are we just making Google bid higher for no meaningful gain?
Based on the data, seasonality adjustments often hurt efficiency and rarely deliver the breakthrough many advertisers expect.
Below is a breakdown of the study and what it means for PPC managers heading into peak season.
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 then measured against a pre-BFCM baseline.
The accounts were grouped into:
- Advertisers who did not use seasonality bid adjustments
- Advertisers who did apply them
Across all three years, consistent patterns emerged from their study.
#1: Smart Bidding already adjusts for BFCM without manual prompts
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 intent and increased bids without needing an external nudge.
#2: Seasonality adjustments inflated CPCs far more than necessary
Seasonality adjustments tell Google’s system to raise bids based on your predicted conversion rate increase.
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%.
And Smart Bidding acts as if you’re exactly right. It usually doesn’t soften that prediction or test into it.
The study showed that 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%
Adjustments consistently doubled CPC inflation, even though Smart Bidding was already raising bids based on real-time conversion signals.
#3: ROAS dropped for advertisers using seasonality adjustments
When CPC increases outpace conversion rate increases, 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%
The “no adjustment” group maintained stable ROAS, even improving in 2024. The “with adjustment” group saw steep declines every year.
Why Do Seasonality Adjustments Struggle During BFCM?
Optmyzr explains this dynamic as a precision issue.
When you apply a seasonality adjustment, you are making a specific prediction about the conversion lift. If you estimate the lift at +40% and the real lift ends up being +32–35%, that gap translates directly into overbidding.
Fred Vallaeys writes:
Smart Bidding takes this literally. It does not hedge your bet. It assumes you have perfect foresight.
That’s the core problem.
Black Friday and Cyber Monday are also in the category of highly predictable retail events. Google has years of historical BFCM data to model expected shifts. As a result, Optmyzr concludes:
Seasonality adjustments work best when Google cannot anticipate the spike.
BFCM is not one of those situations. It’s practically encoded into Google’s models.
The Trade-Off: More Revenue, Lower Efficiency
The study did show that advertisers using seasonality adjustments often drove 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 again, those gains came with notable ROAS declines.
This supports a practical interpretation:
- If your brand’s priority is aggressive market share capture, top-line revenue or inventory liquidation, seasonality adjustments can deliver more volume.
- If your brand’s priority is profitable performance, adjustments tend to work against that goal during BFCM.
When Seasonality Adjustments Do Make Sense
In the study, Optmyzr made it very clear: seasonality adjustments themselves aren’t the problem. The misuse of them is.
They work well in scenarios where you genuinely have more insight into the spike than the platforms do, such as:
- A short flash sale
- A new one-time promotion with no historical precedent
- A large, concentrated email push
- Niche events with little global relevance
Situations where they may not make the most sense:
- Black Friday and Cyber Monday (supported by their data study)
- Christmas shopping windows
- Valentine’s Day for gift categories
These events are already modeled extensively by Google’s bidding systems.
What Should PPC Managers Do With This Data?
If you’re looking to make some changes into your PPC accounts this holiday season, here’s a few ways to apply these findings in a practical way.
#1: Default to not using seasonality adjustments for BFCM
For the majority of advertisers, letting Smart Bidding handle the conversion rate spike naturally leads to steadier ROAS and fewer surprises.
The data supports this approach across three consecutive years.
#2: If leadership insists on volume, be explicit about the trade-off
You can lean on Optmzyr’s findings to set expectations, not just express an opinion.
For example:
- “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 will need to prepare for much lower cost efficiency.”
These examples keep the conversation focused on the business, not just the tactical levers you pull.
#3: Spend your energy on guardrails, not the predictions
In the study, Optmzyr reminds advertisers that trusting the algorithm doesn’t mean blindly letting it run without any oversight.
Instead of guessing the exact uplift, your value during peak season come from:
- Smart budget pacing
- Hourly monitoring (with automated alerts, of course!)
- Bid caps when necessary
- Audience and device segmentation checks
- Creative and offer readiness
These are some of the key areas where human judgment beats prediction.
Final Thoughts On Optmyzr’s Study
Optmyzr’s study doesn’t argue that seasonality bid adjustments are bad. What it does argue is that context is everything.
For predictable, high-volume retail events like BFCM, Google’s bidding systems already have the signal they need. Adding your own forecast often leads to overshooting, inflated CPCs, and unnecessary efficiency loss.
For unique or brand-specific spikes, adjustments remain valuable.
This research gives PPC managers something we rarely get during BFCM: solid data to support a more measured, less reactive approach. If nothing else, it gives you the backup you need the next time someone asks:
“Should we turn on seasonality adjustments this Black Friday?”
Your answer can be confident, data-driven, and clear.
