3-Year Study: The BFCM Bidding Tactic Quietly Killing Your ROAS

Executive snapshot: BFCM seasonality adjustments performance

• Across 2022-2024 BFCM periods, accounts without seasonality adjustments still saw conversion rates rise by 7.5-17.5% as Smart Bidding detected higher intent on its own.[S1][S2]
• CPC inflation was consistently higher when advertisers used seasonality adjustments - roughly double the increase vs. those that did not (for example, +17% vs. +36.7% in 2022).[S1][S2]
• ROAS fell sharply for advertisers using adjustments, dropping 10-17 percentage points more than advertisers who relied on Smart Bidding alone (for example, -2% vs. -17% in 2022).[S1][S2]
• Revenue growth was stronger for the adjustment group - up to +50.5-52.8% vs. +25-33.8% without adjustments - but that growth came with worse efficiency.[S1][S2]

For marketers, this indicates that BFCM seasonality adjustments are mainly a volume lever, not an efficiency lever, and should be framed internally as such.

Method & source notes for the Optmyzr BFCM analysis

Optmyzr, led by Fred Vallaeys, analyzed performance for up to 6,000 Google Ads advertisers per year across three BFCM periods: 2022, 2023, and 2024.[S1][S2] The BFCM window was defined as the Wednesday before Black Friday through the Wednesday after Cyber Monday.[S1] The study compared performance during this window with a pre-BFCM baseline for each year.

Accounts were grouped into two cohorts:[S1][S2]

• Advertisers who used Smart Bidding seasonality adjustments for BFCM
• Advertisers who did not use seasonality adjustments

Key metrics examined included:

• Conversion rate changes vs. baseline
• CPC inflation vs. baseline
• ROAS changes vs. baseline
• Revenue growth vs. baseline

The analysis is observational, not a controlled experiment. Advertisers self-selected into using or not using adjustments, which introduces possible selection bias (for example, more aggressive or larger advertisers may be more likely to use adjustments). Results are also limited to Optmyzr's client base, which may not represent the full Google Ads advertiser population.[S2]

Google's own documentation for Smart Bidding seasonality adjustments notes that they are designed for short, temporary, advertiser-specific events and "not recommended for major holidays" because Smart Bidding already anticipates these.[S3] This aligns with the way Optmyzr interprets its findings.[S1][S2]

Findings on BFCM seasonality adjustment impact across CPC, ROAS, and revenue

Across three BFCM cycles, the Optmyzr dataset shows a repeated pattern: Smart Bidding reacts effectively to BFCM without extra signals, while manual seasonality inputs often overshoot actual conversion lift and inflate CPCs.[S1][S2] The following subsections summarize the main quantitative outcomes.

Smart Bidding without BFCM seasonality adjustments still captured higher intent

For advertisers not using seasonality adjustments, conversion rate during BFCM rose meaningfully vs. the pre-BFCM baseline:[S1][S2]

• 2022: +17.5%
• 2023: +11.9%
• 2024: +7.5%

This indicates that Smart Bidding automatically adjusted bids upward as user intent improved, based on real-time signals and historical BFCM patterns, without manual prompts.[S1][S2] Google's public guidance also states that Smart Bidding already accounts for seasonal events such as major holidays using its models.[S3]

CPCs did rise in this no-adjustment cohort, but at a moderate level:[S1][S2]

• 2022: +17%
• 2023: +16%
• 2024: +17%

ROAS in the no-adjustment group stayed relatively stable:[S1][S2]

• 2022: -2%
• 2023: -1.5%
• 2024: +5.7%

Fact summary: Without applying any manual seasonality uplift, advertisers still saw BFCM-driven conversion gains, moderate CPC inflation, and flat-to-improving ROAS across the three years.[S1][S2]

BFCM seasonality adjustments inflated CPCs and reduced ROAS despite higher revenue

For advertisers who enabled seasonality adjustments, Smart Bidding treated the advertiser's forecast as precise and raised bids immediately by the specified conversion uplift.[S1][S2] Optmyzr notes that the system does not "hedge" these inputs; it assumes the forecast is correct.[S2]

As a result, CPC inflation in the adjustment group was significantly higher than in the non-adjustment cohort:[S1][S2]

• CPC change (no adjustment vs. with adjustment):
• 2022: +17% vs. +36.7%
• 2023: +16% vs. +32%
• 2024: +17% vs. +34%

ROAS performance diverged even more clearly:[S1][S2]

• ROAS change (no adjustment vs. with adjustment):
• 2022: -2% vs. -17%
• 2023: -1.5% vs. -10%
• 2024: +5.7% vs. -15.7%

However, revenue growth was stronger for advertisers who used adjustments, particularly in 2022 and 2023:[S1][S2]

• Revenue growth (no adjustment vs. with adjustment):
• 2022: +25% vs. +50.5%
• 2023: +30.3% vs. +52.8%
• 2024: +33.8% vs. +39.9%

Optmyzr explains this pattern as a precision problem: when the forecasted conversion lift (for example, +40%) exceeds the actual lift (for example, +32-35%), the difference is translated directly into overbidding.[S2] Major events like BFCM and Christmas are heavily represented in Google's historical data, so the platform already has strong priors on likely shifts.[S1][S2][S3]

Fact summary: BFCM seasonality adjustments tended to double CPC inflation, cut ROAS by roughly 10-17 percentage points, and increase revenue growth, especially for brands aggressively prioritizing volume.[S1][S2]

Interpretation & implications for PPC and paid search strategy

Interpretation (Likely): For predictable, widely recognized events such as BFCM, Smart Bidding already has enough history to project conversion-rate spikes. The Optmyzr data and Google's own guidance both indicate that manual seasonality adjustments during these periods often overshoot and reduce efficiency.[S1][S2][S3] Relying on Smart Bidding alone for BFCM is likely to maintain steadier ROAS while still capturing demand.

Implications for strategy:

• Default BFCM stance - avoid adjustments (Likely): For most advertisers, the default should be not to set seasonality adjustments for BFCM and other major holidays. The three-year data shows similar or better ROAS and still-strong revenue growth without them.[S1][S2]
• Use adjustments only when you have unique information (Likely): Seasonality adjustments remain useful for events where Google has little or no prior data: short flash sales, one-off promotions, large email pushes, or niche events that are specific to your brand or category.[S1][S2][S3]
• Treat seasonality adjustments as a conscious trade-off (Likely): If leadership prioritizes top-line revenue, market share gains, or inventory clearance, seasonality adjustments can be justified as a calculated way to drive additional volume at the cost of lower ROAS. The historical impact range from Optmyzr (revenue gains of roughly 15-25 percentage points with ROAS drops of roughly 10-17 percentage points) provides a realistic expectation band for internal planning.[S1][S2]
• Focus human effort on guardrails, not forecasts (Likely): The study supports a shift in human focus away from guessing uplift percentages and toward controls such as:
  • Budget pacing and reallocation during the BFCM window
  • Monitoring and alerting for unexpected CPC or spend spikes
  • Bid caps for sensitive campaigns
  • Checks on search query quality, audiences, and devices
  • Readiness of creative and offers so higher intent converts efficiently[S1][S2]
• Measurement planning remains important (Tentative): While not directly tested in the study, tying BFCM plans to clear ROAS and revenue targets per campaign and channel is likely to make decisions about using or avoiding adjustments more explicit and less reactive.

Contradictions, gaps, and open questions on seasonality bidding

Scope and representativeness: The study covers up to 6,000 advertisers per year but only within Optmyzr's user base.[S1][S2] These advertisers may skew toward more sophisticated or higher-spend accounts, limiting generalization to smaller or less mature accounts.

Selection bias: Advertisers who chose to use seasonality adjustments may differ structurally from those who did not (budget levels, risk tolerance, marketing mix), and those differences could influence both ROAS and revenue outcomes independently of adjustments. The study does not report controls for such factors.[S2]

Lack of granularity: Public reporting of the study aggregates across:[S1][S2]

• Industries and verticals
• Account sizes and budgets
• Geographies and currencies

The results may mask categories or segments where adjustments perform better or worse. No breakdown is provided by match type, device, or campaign type (for example, Performance Max vs. standard search), which could influence how seasonality adjustments behave.

No randomized experiment: There is no indication that advertisers were randomly assigned to use or not use adjustments, nor that individual advertisers ran controlled A/B tests during the same BFCM window. This limits the ability to establish causality, even though the correlations are consistent over three years.[S2]

Interaction with other automation signals: The study does not detail how seasonality adjustments interacted with other automated systems - for example, Performance Max learning patterns, audience signals, or first-party data use. Those factors might affect how much overbidding occurs and how quickly systems normalize after BFCM.

External alignment with Google guidance: Google's guidance already warns against using seasonality adjustments for major holidays.[S3] Optmyzr's results reinforce this but do not quantify whether some refined approaches (for example, lower uplift percentages, tighter time windows) could reduce the negative ROAS impact while still helping brands meet aggressive revenue targets.

Data appendix: summary tables from Optmyzr BFCM seasonality study

Table 1 - Conversion rate change during BFCM vs. pre-BFCM (no seasonality adjustment)[S1][S2]

Table 2 - CPC inflation during BFCM vs. pre-BFCM[S1][S2]

Table 3 - ROAS change during BFCM vs. pre-BFCM[S1][S2]

Table 4 - Revenue growth during BFCM vs. pre-BFCM[S1][S2]

Sources

• [S1] Brooke Osmundson, "What Optmyzr's Three-Year Study Reveals About Seasonality Adjustments During BFCM," Search Engine Journal - article summarizing Optmyzr's study.
• [S2] Optmyzr, "BFCM Seasonality Adjustments Study" - three-year analysis of seasonality adjustments during BFCM, 2022-2024; methodology and cohort descriptions referenced via S1.
• [S3] Google Ads Help, "Seasonality adjustments for Smart Bidding" - guidance on when to use seasonality adjustments and why they are not recommended for major holidays (accessed prior to Oct 2024).