Seasonal noise around Tết and mid-year sales
How we adjust funnel and retention readings when Vietnam’s calendar bends buying behavior.
Tết compresses browsing into short bursts and stretches delivery promises. Mid-year sale events reverse the pattern: long browsing, heavy discounting, and a cohort of buyers who may not return at full price.
For funnel diagnostics spanning these periods, we either split the window or annotate each stage with campaign flags. Comparing a quiet October to a flash-sale June without labels invites the wrong conclusion about checkout quality.
Retention studies should start cohorts after the holiday washout when possible. Buyers acquired in the final shopping week before Tết often behave differently from those acquired in March, even inside the same category.
If leadership needs a single chart for the board, present both the raw series and a seasonally marked version. Honesty about calendar effects builds more trust than a smoothed line that hides the country’s real shopping rhythm.