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ETF buyers carried bitcoin to a 6% gain in a month the dollar rose nearly 2%
Bitcoin gained about 6% in September as the dollar index rose nearly 2% and the 10-year Treasury yield passed 5%. Most of that gain came from a burst of ETF buying, so allocators who treat bitcoin as a bet against the dollar are really underwriting that flow.
The Investor · Invest desk
What happened
- On Sept. 15 the Senate's Clarity Act failed a 49-50 cloture vote, and spot bitcoin ETFs lost $450.4 million, their worst day since June.
- The next day the Federal Reserve raised rates 25 basis points to 3.75%-4%, its first hike since 2023, and bitcoin fell to around $75,000.
- Spot ETFs then took in about $2.98 billion over seven straight sessions, including nearly $1 billion on Sept. 21, their best day since October 2025.
- More than $800 million of short positions were liquidated in 24 hours as bitcoin ran to $87,354, its highest level since late January.
- Last year's green September was followed by a 3.69% loss in October and a 23% drop across the fourth quarter, according to Decrypt.
Compiled by The InvestorSomething wrong?How this is made
Why it matters
- decision A long-dollar hedge held against bitcoin on the inverse assumption gained about 2% while bitcoin gained about 6%, so hedge ratios fitted to that correlation need re-estimating before a falling month tests them.
- contradiction Crypto Briefing's 6.14% sits 1.15 points below the 2024 record that Decrypt's 7.33% would beat, so the "best September" label depends on a single final close.
- constraint The Fed meets again on Oct. 27-28 and Dec. 8-9, so the ETF flow that carried September has two more rate decisions to absorb before year-end, after a hike that first sent bitcoin lower.
Bitcoin opened the month near $78,500. The post-hike low of about $75,000 was a fall of roughly 4.5%, and the climb to $87,354 that followed was about 16.5% off that low [4][7][1][9][2]. The first leg is what an inverse-dollar model predicts. Crypto Briefing ties the dollar index's September gain to hawkish Fed signals, and the 30-year Treasury yield reached levels last seen in 2002 [2][3].
The second leg was ETF money. The $2.98 billion that arrived over seven sessions works out to about $426 million a session, within $25 million of the Sept. 15 outflow, in the opposite direction [3]. Crypto Briefing also counts a record week of inflows approaching $2.4 billion during the quarter [11].
The month supports three readings. Crypto Briefing's is that ETF ownership is changing how bitcoin reacts to traditional indicators, so the inverse link to the dollar may be breaking down [19][11]. Citing analysts it does not name, it adds seller exhaustion [11]. A second is momentum. Bitcoin rose 25% in August and more than 40% from a July low near $58,500 during the third quarter, and September may be the tail of that run [4][13]. The third is that one flow outran the rate signal for a few weeks, and the old relationship returns once the flow slows.
I think the third fits the record best. The hike moved bitcoin down, as the old model says it should, and the recovery began when the ETF buying did [7][8]. The counter-case is that ETF holders are a new class of buyer whose demand does not track the dollar, and one month cannot settle that. The evidence against my view would be a month of flat or negative ETF flows, with the dollar index near 101.61 and the 10-year above 5%, in which bitcoin still holds its late-September range of $83,000 to $84,600 [2][3][20].
If the third reading holds, an allocator long bitcoin is mainly exposed to institutional demand for the ETFs. Crypto Briefing wrote that the open question is whether those inflows can keep offsetting a 10-year yield above 5% [12]. The position has not yet paid for the year. Bitcoin still trades about 4.4% below the roughly $87,497 where it began 2026 [14].
What to watch
- Decrypt's support at $82,626 and the $81,166 to $79,705 zone below it; a close near $79,705 would give back about 62% of the rebound from the post-hike low.
- Brent crude back above $100 after Trump rejected Iran's terms for reopening the Strait of Hormuz; Decrypt reports that move pulled bitcoin to $83,000 on Monday.