Weekly unemployment claims are published seasonally adjusted, and the adjustment factors are known in advance and published by the agency. Around holidays, auto-plant retooling weeks and the start of school terms, the raw-to-adjusted conversion swings enough to move the printed number several thousand in either direction. You forecast the raw number from state-level filings, apply the published factor exactly, and trade the weekly threshold markets on the arithmetic.
Markets on Polymarket where jobless-claims seasonal-factor edge is the natural play: