HKMA: Linked Exchange Rate System Operating Normally; Timing of Weak-Side Convertibility Undertaking Trigger Hard to Predict
nashnova research
HKMA Chief Executive Eddie Yue said on October 6 that the Hong Kong dollar has drifted close to the 7.85 weak-side convertibility undertaking, but the trigger point is hard to predict; the linked exchange rate system's automatic adjustment mechanism is working as designed, and the public should manage interest-rate risk.
How close is the Hong Kong dollar to the line?
From April to May, the HKD traded roughly between 7.8300 and 7.8380 against the USD. It began weakening from mid-June.
Recently it has hovered at 7.8460–7.8475 — only about 25 pips from the weak-side convertibility undertaking at 7.8500.
This means → the currency is already at the weakest edge the system permits. One more step down and the HKMA's automatic buy mechanism kicks in.
Why has the Hong Kong dollar been weakening?
The core driver is a widening HKD-USD interest-rate gap. U.S. rates are higher, so traders borrow cheap HKD to buy USD and pocket the spread — a carry trade.
The second factor is falling HKD demand tied to the stock market. Buying Hong Kong equities requires converting into HKD; a cooler market means less conversion.
Seasonal demand from quarter-end settlements and listed-company dividends has also faded, removing another source of HKD buying.
What role does the Fed play in all this?
The Fed raised rates by 25 basis points at its September meeting. The statement said inflation remains elevated; the chair called policy "still on the accommodative side."
Geopolitical tension, rising energy prices, and the AI investment boom are keeping U.S. growth strong. Markets have broadly raised their U.S. rate-path expectations.
This means → if inflation does not retreat, markets estimate the Fed may hike again between now and mid-2027, widening the HKD-USD gap further and keeping pressure on the Hong Kong dollar.
What happens if the weak-side undertaking is triggered?
In plain terms = once HKD hits 7.85, the HKMA is obligated to buy unlimited HKD and sell USD at that price — a hard commitment written into the system.
The result: the banking system's aggregate balance falls, the interbank rate (HIBOR) gets pushed up, and HKD interest rates rise.
Higher rates narrow the carry-trade spread, money flows back into HKD, and the exchange rate stabilizes. This reflects the linked system's core logic: use automatic interest-rate adjustment to anchor the currency.
What does this mean for ordinary people?
Yue explicitly reminded the public to fully consider and manage interest-rate risk when making property, investment, or borrowing decisions.
This means → if you hold a floating-rate HKD loan — a mortgage, for instance — a trigger of the weak-side undertaking and a rise in HIBOR will directly increase your monthly payment.
The HKMA stressed it will monitor markets closely. The system is designed to cope, but the cost of rising rates falls on borrowers.
市场有风险，内容仅供研究参考，不构成投资建议。