The Hong Kong Monetary Authority intervened six times in eight trading sessions this month, selling a combined US$8.4bn to defend the Hong Kong dollar's 7.85 weak-side convertibility undertaking. The Aggregate Balance — the pool of funds Hong Kong commercial banks hold with the HKMA — fell to HK$46.3bn after Thursday's operation, its lowest since November 2019.
The interventions are mechanical. Under the Linked Exchange Rate System in place since 1983, the HKMA is required to buy Hong Kong dollars from any bank that presents them at 7.85. There is no discretion. The rate holds because the HKMA will spend whatever it takes to hold it.
The question is not whether the peg survives. It will. The Hong Kong government's fiscal reserves and the Exchange Fund back more than HK$4 trillion in Hong Kong dollar liabilities. Speculators who bet against the peg in 1997 lost. George Soros lost money on Hong Kong. What the current pace of interventions reveals is something more specific: the carry trade running through the city is repricing, and the property book sitting on bank balance sheets has not been updated to reflect it.
The carry trade
The US dollar has strengthened against most Asian currencies this year, driven by the Federal Reserve's 5.25–5.50% target rate and a run of hotter-than-expected inflation readings. The HKMA cannot set Hong Kong interest rates independently. HIBOR — the Hong Kong interbank offered rate — should in theory track US rates closely under a fixed exchange regime. This month, the spread between one-month HIBOR and one-month SOFR widened to 87 basis points, against a five-year average of 31 basis points.
That spread is the carry. Banks and funds borrow cheap Hong Kong dollars, convert them to US dollars, and earn the difference. When enough of them do it at once, the Hong Kong dollar falls toward 7.85, the HKMA buys it back, HIBOR rises as liquidity shrinks, and the trade closes. Six interventions in eight sessions suggests the trade is coming in faster than the self-correcting mechanism can absorb it.
HIBOR rose 14 basis points over the two weeks of the current intervention cycle. That feeds directly into mortgage costs. Hong Kong's mortgage market is predominantly HIBOR-linked. A 50 basis-point rise in HIBOR adds roughly HK$1,600 per month to the cost of a HK$6m floating-rate mortgage. At the current pace, a move of that scale is plausible within two to three months.
The property book
The deeper exposure is on bank balance sheets. Hong Kong banks hold an estimated HK$1.8 trillion in mortgage and commercial property loans, according to HKMA supervisory data published in March. The bulk of this exposure was written at 2020 and 2021 valuations, when residential prices were near record highs and commercial rents were recovering from the social unrest of 2019.
Those valuations have not been fully revised. Residential prices have fallen roughly 22% from their 2021 peak, according to the Rating and Valuation Department's private domestic price index for Q1 2026. Commercial property has fared worse: Grade A office vacancy in Central reached 14.2% in April, the highest since 2003, according to JLL Hong Kong data.
[Inference] The gap between loan book valuations and current market prices implies unrealised losses on collateral. The scale depends on individual loan-to-value ratios at origination, which vary by institution and are not publicly disclosed at the loan level. The HKMA has required banks to stress-test against a further 15% price decline. Not all have completed that test publicly.
The 2018 defence cycle — the last time the HKMA spent at this pace — ran for ten months and consumed US$51bn from the Exchange Fund. It ended when the US dollar softened and the HIBOR-SOFR spread compressed naturally. The macro environment this time is different: the Federal Reserve has signalled no rate cuts before Q4 2026, and the carry trade does not need to close.
What follows from here
The Aggregate Balance can absorb further drawdowns. Its floor — the point at which the HKMA would face genuine operational difficulty — is well below current levels. The Exchange Fund holds approximately US$416bn in foreign assets, according to the HKMA's May 2026 monthly statistical bulletin. The peg is not breaking.
But the cost of keeping it is now visible in two places: HIBOR, which rose 14 basis points over the two intervention weeks, and property collateral values, which sit at prices the market no longer agrees with. Each HIBOR tick tightens conditions for the developers whose bonds trade at 8 and 9% and whose covenant headroom is measured in tenths of a turn.
Six interventions in eight sessions is a signal about who pays. The peg will hold. The Aggregate Balance will recover when the carry trade closes. The property book will take longer.