Black Friday’s Broken Seasonality Adjustments
▼ Summary
– Google’s seasonality bid adjustments during Black Friday and Cyber Monday consistently harm advertising efficiency despite platform recommendations.
– Smart Bidding autonomously detects BFCM conversion rate increases and maintains stable ROAS without manual adjustments.
– Using seasonality adjustments causes CPCs to surge faster than conversion rates, leading to double-digit ROAS drops.
– These adjustments only benefit advertisers prioritizing pure revenue growth over efficiency, as they deliver higher volume at the cost of margins.
– Seasonality adjustments should be reserved for unpredictable brand-specific events rather than major holidays where Smart Bidding already performs optimally.
A three-year study examining data from thousands of advertisers reveals that applying Google’s seasonality bid adjustments during Black Friday and Cyber Monday often reduces campaign efficiency, despite platform recommendations. The research, analyzing tens of billions of impressions, demonstrates that Smart Bidding algorithms independently recognize and respond to holiday conversion surges without manual intervention.
Smart Bidding’s machine learning models are built to predict and capitalize on recurring retail traffic patterns. When advertisers refrain from applying seasonality adjustments, the system naturally identifies the Black Friday and Cyber Monday conversion lift, raises bids in a measured way, and maintains or even improves return on ad spend. In contrast, accounts using seasonality adjustments experienced cost-per-click inflation that outpaced actual conversion rate gains, directly harming efficiency.
The fundamental issue lies in how Smart Bidding interprets seasonality adjustments. These adjustments essentially instruct Google to anticipate a specific percentage increase in conversion rates and bid more aggressively to capture it. However, the system takes these projections literally. If an advertiser overestimates the conversion lift, which happens frequently, the algorithm responds by overbidding. For example, predicting a 50% conversion rate increase when the actual lift is only 40% results in effectively overbidding by more than 7%. During high-volume periods like Black Friday, even minor miscalculations rapidly accumulate into significant wasted spend.
Three consecutive years of data tell a consistent story. First, Smart Bidding consistently detected the holiday conversion spike on its own, with measured lifts of 17.5% in 2022, 11.9% in 2023, and 7.5% in 2024. Second, cost-per-click increases were approximately double when seasonality adjustments were applied compared to letting the algorithm work autonomously. Third, advertisers who trusted Smart Bidding without adjustments maintained stable or improved ROAS, while those using seasonality adjustments frequently saw double-digit percentage declines.
There is one scenario where seasonality adjustments prove beneficial: when the primary objective is revenue growth at any cost, regardless of efficiency. Across all three years studied, advertisers using adjustments achieved higher revenue lifts, sometimes dramatically so, compared to those relying solely on Smart Bidding. The trade-off is clear: volume increases while efficiency metrics deteriorate.
Seasonality adjustments make strategic sense only when Google lacks advance signals about upcoming demand shifts. They work well for unpredictable events like flash sales, email-exclusive promotions, surprise clearance events, or niche seasonal patterns that lack historical precedent. For widely anticipated retail holidays including Black Friday, Cyber Monday, Christmas, and Valentine’s Day, events with years of predictable data, these adjustments typically introduce more volatility than value.
The critical insight for marketers is that Google’s algorithms already recognize it’s Black Friday. Smart Bidding trains on extensive historical data from previous holiday seasons and reliably identifies conversion rate increases without manual guidance. Overriding the system often triggers aggressive overbidding, inflated costs, and diminished returns, meaning many advertisers unintentionally waste budget during the year’s most competitive shopping period.
Understanding when Smart Bidding already possesses sufficient signal enables advertisers to avoid costly errors, protect campaign efficiency, and reserve seasonality adjustments for situations where they genuinely create advantage. The evidence strongly suggests that for major retail holidays, Smart Bidding performs better without interference. The smarter approach involves trusting the algorithm while implementing protective measures like anomaly alerts, pacing monitors, and bid caps, these provide necessary oversight without disrupting the bidding model’s core functionality.
(Source: Search Engine Land)
