Adjusted Into Irrelevance: How Seasonal Correction Methods Are Quietly Distorting the Trends You Trust
Seasonal adjustment is presented to researchers as a neutral technical step, but the choices embedded in X-13ARIMA-SEATS and related protocols can manufacture apparent trends where none exist—or erase real ones. This article examines which datasets and industries carry the highest risk of seasonal adjustment artifacts, and what practitioners must verify before treating any year-over-year comparison as meaningful.