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Why Seasonality Adjustments Mislead Advertisers on Black Friday

```json { "alt": "Black Friday sale text with red tag on left and a chart with magnifying glass on right.", "caption": "Dive into Black Friday deals with insights at your fingertips. Explore market trends and super savings side-by-side!", "description": "The image features 'Black Friday Sale' text alongside a red tag on a black background, symbolizing shopping deals. On the right, a chart with various colored segments and a magnifying glass signifies analysis and market trends. The combination highlights the synergy between smart shopping and data-driven insights, perfect for e-commerce strategies and customer engagement during sale events." } ```

Written by

shivamcrushpressai

in

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I recently came across a fascinating study highlighting how seasonality adjustments can actually backfire for advertisers during Black Friday, driving up costs and reducing efficiency.

A thorough analysis over three years, involving up to 6,000 advertisers, indicates that using Google’s seasonality bid adjustments during Black Friday and Cyber Monday (BFCM) often undermines efficiency, despite the platforms recommending them.

The big picture. Smart Bidding models are crafted to foresee predictable retail surges. Optmyzr analyzed tens of billions of impressions between 2022 and 2024, finding that advertisers who avoided seasonality adjustments usually had better efficiency metrics.

Without adjustments, Smart Bidding:

  • Recognized the BFCM conversion lift independently
  • Increased bids rationally
  • Maintained stable or improved ROAS, particularly in 2024

With adjustments: CPCs surged faster than the actual conversion rates, eroding efficiency.

Reality check: Google doesn’t need your “heads up.” Seasonality adjustments prompt Google to expect a conversion rate rise and to bid accordingly. If your prediction is off—and it usually is—Smart Bidding overshoots.

For example:

  • You predict a +50% CVR lift
  • The actual lift is +40%
  • This results in an overbid of about 7.1%

During BFCM’s high sales volumes, even minor mistakes become costly quickly.

The data: 3 years of the same story

```json { "alt": "Table showing CPC inflation from 2022 to 2024 with and without seasonal bid adjustment.", "caption": "A comparison of CPC inflation rates over three years reveals significant seasonal adjustments.", "description": "This table illustrates the CPC inflation rates from 2022 to 2024, comparing figures with and without seasonal bid adjustments. In 2022, CPC inflation without adjustment is 17%, increasing to 36.7% with adjustment. For 2023, the rates are 16% without adjustment and 32% with adjustment. In 2024, both rates without and with adjustment are 17% and 34%, respectively. This data highlights the impact of seasonal adjustments on advertising costs, a crucial insight for marketers and advertisers." } ```

1. Smart Bidding already adjusts for the CVR spike

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

No additional guidance needed.

2. CPC inflation doubles with adjustments

Across all observed years, CPCs increased approximately twice as much when a seasonal adjustment was used.

3. ROAS drops significantly

Advertisers relying on Smart Bidding saw stable or improved ROAS, whereas those who intervened suffered double-digit losses.

The one exception: “Volume at all costs.” If the aim is pure revenue growth, disregarding margins, seasonality adjustments can be beneficial.

Revenue lifts were notably higher with adjustments:

  • 2022: +50.5% vs. +25.0%
  • 2023: +52.8% vs. +30.3%
  • 2024: +39.9% vs. +33.8%
```json { "alt": "Table showing revenue growth from 2022 to 2024 with and without seasonal bid adjustment with related trade-offs.", "caption": "Seasonal bid adjustments impact revenue growth significantly, but come with trade-offs in ROAS, as shown from 2022 to 2024.", "description": "This table presents a comparison of revenue growth from 2022 to 2024, analyzing scenarios with and without seasonal bid adjustments. In 2022, a 25% growth without adjustment jumps to 50.5% with it, though ROAS drops by 17%. In 2023, adjustments raise growth from 30.3% to 52.8%, with a 10% ROAS decline. By 2024, growth is 33.8% without and 39.9% with adjustment, noting a 16% ROAS reduction. Keywords: seasonal bid adjustment, revenue growth, ROAS, trade-off." } ```

Efficiency may decline, but volume certainly increases.

When seasonality adjustments make sense. They’re useful when Google doesn’t have prior signals, like one-off or niche events.

Good for:

  • One-time flash sales
  • Email-only offers
  • Surprise clearance sales
  • Niche seasonal spikes

Not recommended for:

  • Black Friday
  • Cyber Monday
  • Christmas
  • Valentine’s Day
  • Any event with a predictable historic pattern

Why we care. Google already recognizes the significance of Black Friday. Smart Bidding is trained with years of BFCM data and can detect conversion rate spikes independently. Overriding this can lead to excessive bidding, increased CPCs, and reduced ROAS, so many marketers might be wasting their budget during this crucial week.

By recognizing when Smart Bidding has an adequate signal, advertisers can avoid expensive errors, maintain efficiency, and reserve seasonality adjustments for when they add true value.

Bottom line. Smart Bidding effectively manages major retail holidays. Seasonality adjustments often bring more chaos than benefits during predictable retail peaks. Keep them for unique, brand-specific events that Google can’t predict.

Smart move: Trust the algorithm — use tools like anomaly alerts, pacing monitors, and bid caps for control without conflicting with Smart Bidding’s core models.

Dig Deeper. Do Seasonality Adjustments Actually Help During BFCM? A 3-Year Study Says No.

Inspired by this post on Search Engine Land.

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FAQs

Why can seasonality adjustments mislead advertisers on Black Friday?

The article says Smart Bidding already recognizes predictable Black Friday and Cyber Monday conversion lifts. Adding a seasonality adjustment can make bids rise faster than actual conversion rates, increasing CPCs and reducing ROAS.

Does Google Smart Bidding already account for BFCM conversion spikes?

Yes. The post says Smart Bidding is trained on years of BFCM data and can detect conversion rate spikes independently, with observed CVR adjustments in 2022, 2023, and 2024.

What happens to CPCs when advertisers use seasonal bid adjustments during BFCM?

Across the observed years, CPCs increased approximately twice as much when seasonal bid adjustments were used. The article notes that this faster CPC inflation eroded efficiency.

When can seasonality adjustments still make sense?

They can be useful when Google lacks prior signals, such as one-time flash sales, email-only offers, surprise clearance sales, or niche seasonal spikes. The post recommends reserving them for unique, brand-specific events that Google cannot predict.

Are seasonality adjustments ever useful for Black Friday revenue growth?

The article identifies one exception: volume at all costs. Revenue lifts were higher with adjustments in the cited years, but the trade-off was lower efficiency and reduced ROAS.

What should advertisers use instead of overriding Smart Bidding on predictable holidays?

The post suggests trusting the algorithm for predictable retail holidays and using controls such as anomaly alerts, pacing monitors, and bid caps. These tools provide oversight without conflicting with Smart Bidding’s core models.

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