Optmyzr study: seasonality adjustments backfire on Black Friday, cutting ROAS by 15% while raising CPCs 34%
TLDR
Optmyzr's analysis of 5,886 Google Ads accounts over three years found that seasonality adjustments consistently backfire during Black Friday, raising CPCs while cutting ROAS compared to letting Smart Bidding manage the period unsupervised.
Optmyzr analyzed over 5,800 Google Ads accounts across 2022–2024 Black Friday periods and found that advertisers using seasonality adjustments saw CPCs rise 34%—double the 17% increase for those who didn't—while ROAS fell 15.7% versus a 5.7% rise for non-adjusters. The data showed the conversion-rate bump from Black Friday has shrunk from 17.5% (2022) to 7.5% (2024) as shoppers spread purchases across longer promotional windows, making preset adjustment predictions consistently overoptimistic. Google's Smart Bidding already anticipates Black Friday from historical patterns and real-time auction signals, so manual adjustments stack expectations on top of existing ones; the firm recommends using adjustments only for unpredictable events (flash sales, niche promotions) and replacing overrides with lower target ROAS settings or pre-sale guardrails instead.