Monetary Base
Also: M0, base money
economics · intermediate
The most liquid form of money in an economy — for fiat, central-bank reserves plus cash; for Bitcoin, all coins ever mined.
Different aggregates measure different layers: M0 (base), M1 (M0 + demand deposits), M2 (M1 + savings and time deposits). Bitcoin has exactly one aggregate, defined by the issuance schedule. Currently around 19.8 million BTC, asymptoting to 21 million by ~2140.
The distinction matters because most "dollars" in circulation aren't base money — they're credit money created by commercial banks through fractional reserve lending. M2 in the US sits around $21 trillion as of 2025; M0 is about $5.5 trillion. The Fed controls base money directly; the wider aggregates depend on bank behavior and credit demand.
Bitcoin's collapsed structure (no fractional-reserve issuance possible at the base layer) is what gives the 21-million cap teeth. Lightning, Liquid, statechains, and fedimint can layer credit and IOUs on top of Bitcoin, but they cannot inflate the base money. That's the architectural feature, not a policy choice.