Optmyzr’s Three-Year Study Reveals Risks of Seasonality Adjustments During BFCM

A new Optmyzr’s three-year study reveals risks of seasonality adjustments during Black Friday–Cyber Monday BFCM campaigns.

Every holiday season, many PPC experts advise using seasonality bid adjustments to prepare for Black Friday and Cyber Monday (BFCM). The logic seems straightforward as conversion rates climb during peak shopping days, manually signaling Google’s Smart Bidding to ramp up bids could capture more sales.

But Optmyzr’s recent three-year analysis challenges this widely held belief.

Study Setup and Objective

From 2022 to 2024, Optmyzr’s team, led by Fred Vallaeys, reviewed performance data from up to 6,000 advertisers each year during the BFCM period, which runs from the Wednesday before Black Friday through the Wednesday after Cyber Monday.

They compared two groups:

• Those who implemented seasonality bid adjustments.
• Those who did not.

The central question was whether these adjustments genuinely drive better results or simply cause higher costs with limited benefit.

Smart Bidding Handles BFCM Spikes Naturally

The data showed that Smart Bidding effectively responds to conversion surges without needing manual intervention.

Advertisers who skipped seasonality adjustments still experienced conversion rate increases of:

• 17.5% in 2022.
• 11.9% in 2023.
• 7.5% in 2024.

As Vallaeys explained, “the algorithm did exactly what it was designed to do,” detecting higher purchase intent and raising bids accordingly.

Seasonality Adjustments Lead to Excessive CPC Inflation

Manual seasonality bids instruct Google’s system to immediately raise bids in proportion to expected conversion rate increases, but the algorithm treats this forecast as exact and rarely attempts moderation.

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%.

This caused cost-per-click (CPC) inflation to almost double compared to accounts without adjustments:

• 2022: +17% vs. +36.7%
• 2023: +16% vs. +32%
• 2024: +17% vs. +34%

This sharp cost rise often outpaced actual conversion gains, eroding profitability.

ROAS Declines for Advertisers Using Adjustments

With CPCs rising faster than conversions, return on ad spend (ROAS) dropped significantly in the adjustment group each year:

• 2022: -17% ROAS with adjustments vs. -2% without
• 2023: -10% vs. -1.5%
• 2024: -15.7% vs. +5.7%

Advertisers who trusted Smart Bidding alone enjoyed steadier or improved ROAS, underscoring the efficiency loss from overbidding.

Why Seasonality Adjustments Falter During BFCM

Optmyzr points to a “precision issue”: manual adjustments require predicting conversion lift accurately.

If you forecast a 40% lift but reality is 32–35%, Google’s bidding aggressively overshoots.

As Vallaeys notes:

“Smart Bidding takes this literally. It does not hedge your bet. It assumes you have perfect foresight.“

Because BFCM is a highly predictable retail event with years of historical data baked into Google’s models, manual seasonality adjustments often duplicate what the system already knows.

The Revenue vs. Efficiency Trade-Off

Though seasonality adjustments frequently boost revenue growth sometimes by nearly double compared to no adjustments this often comes with a steep efficiency cost. For example:

• 2022: +25% vs. +50.5%
• 2023: +30.3% vs. +52.8%
• 2024: +33.8% vs. 39.9%

This suggests adjustments may be suitable for aggressive market-share expansion or inventory clearance, but they usually harm profitable performance.

When Seasonality Adjustments Make Sense

Optmyzr clarifies that seasonality adjustments aren’t inherently flawed; their misuse is the issue. They are valuable when you possess unique insights beyond platform data, such as during:

• Short flash sales
• One-time promotions without historical precedent
• Large, focused email campaigns
• Niche events with limited global reach

For broadly modeled events like:

• Black Friday and Cyber Monday (supported by their data study)
• Christmas shopping windows
• Valentine’s Day for gift categories

Google’s algorithm generally anticipates demand spikes.

Practical Advice for PPC Managers

Given the data, a few strategic pointers emerge:

• Avoid seasonality adjustments during BFCM for most advertisers. Smart Bidding naturally adjusts and maintains ROAS stability.
• If leadership prioritizes volume over efficiency, use Optmyzr’s data to frame realistic expectations about revenue gains coming with ROAS drops.
• Focus human expertise on campaign oversight: pacing budgets, monitoring hourly trends, setting bid caps, segmenting audiences, and ensuring creative readiness. 

These guardrails outperform crude uplift guesses.

Context Is Key

Optmyzr’s study is a reminder that “context is everything.” They show that Google’s bidding systems are well-equipped to handle predictable, high-volume events, so external seasonality bets often lead to costly overspending.

Yet adjustments remain useful when you have genuine, campaign-specific intelligence that the algorithm lacks.

This research arms PPC professionals with data-backed confidence to make more measured, less reactive decisions during BFCM peak seasons.

Final Thought

Next time, when the question arises that “Should we enable seasonality adjustments this Black Friday?” you’ll have a clear, informed answer grounded in robust data.