The insight: Amazon’s decision to double the length of its Prime Day sale delivered significant rewards for its advertising business—as we said it would.

Total ad spending over the four-day event rose 48% YoY, per Pacvue. That outpaced the 34% increase in average brand sales during the period.

Behind the numbers: While topline growth was strong, both average daily spending and average daily sales fell significantly—a sign that both sellers and shoppers were recalibrating their behavior to accommodate the longer event.

• Average daily ad spending fell 26% YoY, according to Pacvue’s analysis, reflecting sellers’ needs to stretch their budgets over a longer period of time.
• Early data from Tinuiti showed that ad costs fell during the first two days, with sponsored product ads’ cost per click down 10% YoY and aggregated demand sale price CPMs down 23%.
• With the four-day event reducing some of the urgency for consumers to buy, advertisers may have opted to concentrate more of their spending on the last two days, when impulse purchases were more likely to occur.

The takeaway: The first four-day Prime Day was an important learning experience for brands. With the event unlikely to get any shorter, sellers will need to be more precise about their ad strategy—focusing spending on times of day when shoppers are more likely to buy, or saving the bulk of their budgets for end-of-sale urgency.

Go further: Read our Amazon Prime Day 2025 report.

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