Prices

Top-card indices take, on each sampling date, the cards with the highest prior prices (225 across all titles for the duelist.jp 225; 100 per title) and move by the change in their total price. Selecting on prior prices avoids look-ahead bias. First sampling date = 1,000. Weights are each constituent's share of the latest total price.

A chained Jevons index over all cards we price: on each sampling date, the index moves by the geometric mean of price relatives for cards with a prior observation. The first sampling date equals 1,000. Unlike the price-weighted Nikkei average, each card's move counts equally, so a single expensive card cannot dominate. Prices are public Japanese shop listings (raw).