M4: Ninja Spinner

30d

-13.9%

90d

-28.7%

1y

-67.0%

All

-67.0%

Level

24.1

Weekly chain-linked index. Each step compares only cards priced in BOTH of the two weeks, so items appearing or delisting cannot move the line — 10.6% of a fixed basket went dark over the last eleven months, and a level computed over whoever reported today would follow that instead of prices. An item must clear $5 in both weeks of a step to count: without a floor, penny rounding dominates. The line is the longest unbroken run of weeks with enough matched pairs — a week too thin to measure truncates it rather than being bridged over. Scoped to this set, using the same construction as the market index. How this is built.