Bitfinex Analysis: BTC Breaks Below Key Support, ETFs See Single-Day Net Outflow of $450 Million

According to Bitfinex Alpha, Bitcoin broke below the key support level of $77,100 on September 15, closing at $75,702 with a daily decline of 3.2%, marking its third consecutive closing lower after breaking through the recent range bottom. On that day, US spot Bitcoin ETFs recorded a net outflow of $450.4 million, with Fidelity FBTC seeing an outflow of $214.8 million and BlackRock IBIT recording an outflow of $161.7 million, accounting for 84% of total outflows. This marks the 14th-largest single-day net outflow in 2026. The downturn was driven by multiple factors: the failure of the CLARITY Act to advance, the 10-year US Treasury yield rising to 5% (for the first time since 2023), accelerated selling by short-term holders (exchange inflows surged sharply from 19,400 BTC to 33,100 BTC, of which 23,200 BTC were acquired at a loss), and foreign demand dropping to a historic low during the 20-year US Treasury auction. From a technical standpoint, BTC has fallen below the market average value of $76,500 and Strategy's average holding price of $75,412, leaving the average holder currently underwater. If the downtrend continues, key support levels below are $73,500 (cost basis for 3-6 month holders) and $71,300 (realized price for short-term holders). A rebound requires reclaiming $77,100 backed by significant spot trading volume.