Analyzing Hong Kong's Linked Exchange Rate: Interest Rate Pass-Through and Market Impacts

1. Event Background: The Facts of the Rate Adjustment

After the US Federal Reserve announced a 50 basis point cut to the federal funds rate target range, bringing it down to 4.75%–5.00%, the Hong Kong Monetary Authority (HKMA) immediately followed suit. Under its preset formula, the HKMA lowered the Base Rate from 5.75% to 5.25%, a matching 50 basis point reduction. This marked the Fed’s first rate cut since March 2020 and the HKMA’s synchronized response within the framework of the Linked Exchange Rate System (LERS).

Chronologically, the HKMA’s adjustment is not an independent policy decision but a “formulaic” reaction mandated by the港元-USD peg. The Base Rate is calculated using a predefined formula: it is set at either 50 basis points above the lower bound of the US federal funds rate target range, or the average of the five-day moving averages of the overnight and one-month Hong Kong Interbank Offered Rates (HIBOR), whichever is higher. Consequently, when the Fed cuts rates, the adjustment to Hong Kong’s Base Rate is essentially triggered automatically.

It is worth noting that there is a significant transmission lag and magnitude difference between the Base Rate adjustment and the commercial banks’ Best Lending Rate (BLR). Major banks, including HSBC, Bank of China (Hong Kong), and Standard Chartered (Hong Kong), announced a 25 basis point reduction in their HKD BLR, lowering it from 5.875% to 5.625%. This adjustment is exactly half the HKMA’s reduction, reflecting the commercial banks’ independence and prudential approach in rate decision-making.

2. Linked Exchange Rate System: The Institutional Root of Rate Linkage

To understand why Hong Kong’s interest rates follow US rate movements, one must examine the core institutional arrangement of the Linked Exchange Rate System.

Hong Kong has implemented the LERS since 1983. Its core mechanism fixes the HKD exchange rate within a trading band of 7.75 to 7.85 HKD per USD. Under this system, the HKMA relinquishes an independent monetary policy space; interest rate levels are largely determined by USD interest rates. Specifically, when USD rates change, capital flows cross-border seeking higher yields, pushing HKD interest rates to align with USD rates to maintain exchange rate stability.

The economic logic behind this mechanism lies in the “interest rate parity” condition. If HKD rates were significantly lower than USD rates, investors would convert HKD to USD for higher returns, putting downward pressure on the HKD exchange rate. Conversely, if HKD rates were notably higher, capital would flow into HKD assets, driving the exchange rate up. To keep the exchange rate within the target band, Hong Kong’s interest rates must move in lockstep with USD rates.

Within this institutional framework, the Fed’s monetary policy adjustments act as an external constraint on Hong Kong’s interest rate policy. The HKMA’s Base Rate adjustment is not based on local economic conditions but serves as a technical safeguard for the LERS. Understanding this premise is critical to interpreting the policy signals released.

3. Base Rate vs. Best Lending Rate: Two Distinct Tiers

In general discourse, the “Base Rate” and the “Best Lending Rate” are often conflated, yet their definitions and functions differ significantly.

The Base Rate is the policy rate set by the HKMA, primarily serving as the benchmark for the discount window. It determines the cost for commercial banks to obtain short-term liquidity from the HKMA, acting as an operational tool for monetary policy. Adjustments to the Base Rate directly impact interbank lending rates but affect retail depositors and borrowers only indirectly.

The Best Lending Rate (BLR), on the other hand, is an optimal lending rate independently set by commercial banks for their customers, acting as a pricing benchmark for retail banking. In Hong Kong, the BLR is widely used in pricing mortgages, corporate loans, and other credit products. Many mortgage rate terms are explicitly expressed as “BLR minus a certain spread,” meaning BLR fluctuations directly affect a borrower’s monthly repayment.

The transmission chain can be summarized as: Base Rate adjustment -> interbank market rate change -> bank funding cost change -> bank adjusts BLR. However, this transmission is neither mechanical nor strictly proportional. When deciding whether to adjust the BLR and by how much, banks comprehensively weigh multiple factors, including their funding cost structure, deposit competition, loan demand, and net interest margin (NIM) pressures.

4. Why Was the Bank BLR Cut Smaller Than the Base Rate?

In this recent adjustment, the HKMA cut the Base Rate by 50 basis points, while major banks reduced their BLR by only 25 basis points. This asymmetry warrants closer analysis.

During past rate hike cycles, Hong Kong banks also did not fully match the Fed’s hike magnitudes. The fundamental reason lies in the unique liquidity conditions of the Hong Kong banking system. When system liquidity is abundant (i.e., supply exceeds demand in the interbank market), interbank lending rates often fall below the US federal funds rate, meaning banks’ funding costs do not rise significantly. Under such conditions, banks lack the incentive to raise their BLR proportionally.

Similarly, in a rate cut cycle, although the Base Rate dropped by 50 basis points, if the banking system’s HKD funding costs had not previously reached the same level as the Base Rate, a 25 basis point reduction in the BLR is sufficient to maintain a reasonable NIM. Banks must strike a balance between “stimulating loan demand” and “protecting their NIM.”

Furthermore, competition in the deposit market is a crucial consideration. If banks aggressively cut the BLR while deposit rate adjustments lag, their NIMs will be compressed. Given that deposit competition remains relatively intense, banks tend to adopt a more conservative pace for rate cuts.

5. Impact on the Deposit Market: Transmission and Divergence

On the deposit side, the transmission of rate adjustments exhibits clear structural differences.

For time deposits, particularly new-funds time deposits, banks flexibly adjust rates based on market funding needs and their liquidity management strategies. In a rate cut cycle, banks typically prioritize cutting new-funds time deposit rates, as new funds are relatively less sensitive to rate changes, granting banks greater pricing autonomy. Existing time deposits have locked-in rates until maturity, meaning adjustments lag.

For savings accounts, rate adjustments are usually linked to the BLR. When the BLR is reduced by 25 basis points, major banks’ savings rates often correspondingly decrease, though the exact magnitude depends on individual bank pricing strategies. Some banks may opt not to adjust synchronously to retain their deposit base.

From a depositor’s perspective, a rate cut implies declining deposit yields. This impact is more direct for groups relying on deposit interest income, such as retirees. In a falling rate environment, depositors may adjust the term structure of their deposits—such as lengthening the duration to lock in currently higher rates—to mitigate the decline in returns.

6. Impact Mechanism on the Hong Kong Stock Market

The Hong Kong stock market is significantly more sensitive to Fed rate changes than mainland Chinese markets, a divergence that also stems from the constraints of the LERS.

Under the LERS, Hong Kong’s liquidity environment is highly integrated with international capital markets. When the Fed cuts rates, USD liquidity tends to loosen, global risk appetite generally rises, and capital flows toward emerging markets and riskier assets. As an international financial center, Hong Kong serves as a primary gateway for capital entering and exiting the Asia-Pacific region, thus often benefiting early from improvements in global liquidity.

The specific transmission paths can be categorized into three levels:

Valuation Level: The risk-free rate is a core variable in asset pricing models. When interest rates fall, the discount rate for future cash flows decreases, theoretically lifting the reasonable valuation level of equities. This effect is particularly pronounced for growth companies and high-valuation sectors.

Capital Flow Level: Rate cuts reduce the cost of holding USD, potentially prompting capital to rebalance from USD assets to non-USD assets. Because the HKD is pegged to the USD, the Hong Kong market carries lower exchange rate risk uncertainty, making it attractive to USD funds seeking risk diversification.

Fundamentals Level: Rate cuts lower corporate financing costs and debt repayment pressures, helping to improve earnings expectations. This effect is transmitted more directly to interest-rate-sensitive sectors heavily represented in the Hong Kong market, such as real estate and finance.

However, it is important to note that Hong Kong stock market performance is not dictated solely by interest rates. Corporate earnings fundamentals, geopolitical risks, and market sentiment also play vital roles. Falling rates provide a supportive condition, not a sufficient one. The recent relative strength of the Hong Kong market, beyond marginal improvements in rate expectations, has been driven by multiple overlapping factors.

7. Policy Signal Implications Under the LERS

The signal released by the HKMA’s synchronized rate cut must be interpreted within the institutional framework.

First, this operation does not represent an independent assessment of local economic conditions. Under the LERS, rate adjustments are primarily responses to external constraints rather than proactive monetary policy operations. Therefore, interpreting Hong Kong’s rate cut as a “policy shift to stimulate the local economy” is inaccurate.

Second, the rate linkage itself reinforces the credibility of the LERS. By strictly executing the preset formula to adjust the Base Rate, the HKMA sends a clear signal to the market about its commitment to maintaining the stability of the linked exchange rate. For international investors, this institutional predictability is a crucial component of the Hong Kong financial system’s appeal.

Third, the incomplete pass-through to commercial bank BLRs reflects a “buffer zone” within Hong Kong’s interest rate system. The independent pricing decisions of commercial banks provide a certain buffer for the local economy, ensuring that rate adjustments do not transmit directly and fully to the real economy. This “two-tier interest rate system” partially mitigates the loss of monetary policy independence inherent in the LERS.

8. Key Indicators for Future Rate Trajectories

Looking ahead at the interest rate path, several dimensions warrant continuous observation:

The Fed’s Policy Pace: As an external constraint, the magnitude and frequency of subsequent Fed rate cuts will directly dictate the adjustment trajectory of Hong Kong’s Base Rate. Current market views on the Fed’s future path diverge; it is necessary to monitor the evolution of key indicators such as inflation and employment data.

Hong Kong Banking System Liquidity: The spread between HIBOR and USD rates reflects the tightness of local liquidity. If HKD liquidity remains abundant, banks’ BLR adjustments may continue to be smaller than Base Rate adjustments. Conversely, if liquidity tightens, banks’ pass-through magnitude may increase.

Supply and Demand in Credit Markets: Changes in bank loan demand will influence banks’ motivations to adjust rates. If rate cuts effectively stimulate mortgage and corporate loan demand, banks may be more inclined to accept narrower NIMs to achieve scale growth.

Operational Status of the LERS: The strength of the HKD exchange rate is a key indicator of system pressure. If the HKD consistently trades near the strong-side convertibility undertaking level, it indicates significant capital inflow pressures and loose liquidity. If the exchange rate weakens toward the weak-side convertibility undertaking, it may trigger capital outflows and liquidity tightening.

9. Conclusion

The HKMA’s 50 basis point reduction in the Base Rate, following the Fed, is a routine manifestation of the interest rate linkage mechanism under the LERS. Its signaling significance lies primarily in maintaining institutional stability rather than representing an aggressive shift in local economic policy. The commercial banks’ 25 basis point follow-through on their BLRs illustrates the independent pricing space and buffer mechanism during the rate transmission process.

For market participants, the correct way to understand this event is to separate the institutional linkage from the commercial banks’ autonomous pricing. The LERS dictates that the “skeleton” of Hong Kong’s interest rates must remain consistent with the US, while the banking system’s liquidity conditions and competitive landscape provide the “muscle” and “buffer” for rate changes. Against the backdrop of a downward interest rate channel, the valuation support effect in the Hong Kong stock market, the pressure of declining deposit yields, and the marginal improvement in borrowing costs will all gradually unfold within this institutional framework.