The 'realized' capitalization: instead of valuing each bitcoin at today's price, it is valued at the price it had the last time it moved on-chain. The market's aggregate 'cost basis', in billions of dollars.
When it rises, fresh capital anchors at higher prices (structural demand); when it stalls, little new capital enters. It underpins MVRV and NUPL. Limits: it is a LEVEL (not an oscillator, no fixed thresholds); it reacts slowly (many coins sleep); it is biased upward by lost or very old coins valued at negligible prices; and it depends on price-history quality. Introduced by Nic Carter and Antoine Le Calvez (Coin Metrics, 2018), from an idea by Pierre Rochard.