According to the source, institutional BTC is primarily held by public companies, spot ETFs, investment funds, and sovereign entities, while most of the overall Bitcoin supply remains untracked by public disclosures, limiting visibility into free float. According to the source post, this concentration in reportable vehicles alongside a large untracked base implies tighter visible liquidity, where incremental ETF net inflows or outflows can disproportionately impact BTC price discovery. According to the source, traders should monitor ETF flow data, exchange balance trends, and futures basis as confirmation signals of supply constraints affecting slippage, spreads, and breakout sustainability.