Hong Kong Currency Defenses Stir Borrowing Cost Volatility Fears

The Hong Kong dollar is nearing the weak end of its trading band, prompting strategists to warn that currency defenses could spark sudden jumps in borrowing costs as cash reserves sit close to historical lows. The local currency moves within striking range of its 7.75 to 7.85 band against the US dollar because higher Treasury yields push traders to prefer the greenback.

Market Interventions

To keep the currency from breaking its weak-side limit, the Hong Kong Monetary Authority buys local dollars. This action drains an interbank cash buffer known as the aggregate balance. The aggregate balance has dropped to HK$54 billion, which equals $6.9 billion. This level was only crossed once before in 2023 during heavy currency defense periods, according to HKMA data. Strategists warn that such a thin cash buffer means even small interventions by the HKMA could cause sharp jumps in local borrowing costs.

Expert Warnings

Carie Li, a strategist at DBS Bank in Hong Kong, states that overall interbank offered rates are set to trend upward and could see volatility if the aggregate balance falls to past lows. The HKMA has already warned the public to manage interest-rate risks for property purchases, investments, and borrowing as the currency nears its limit. Wednesday saw the local currency trade about 17 pips away from the 7.85 boundary. Oversea-Chinese Banking Corp. expects the HKMA might shift liquidity back into the interbank market if cash drains too fast, though this could create two-way rate swings.

Broader Impact

The one-month Hibor has dropped to around 2.7% from a nine-month high of 3.02% reached in late September. Morgan Stanley analysts, led by Jenny Zheng, note that while the low aggregate balance brings back memories of 2022 to 2023 when aggressive Fed rate hikes and interventions pushed up mortgage costs, broader banking buffers remain much healthier today. The aggregate balance makes up just 2.6% of the monetary base.

Context

Central banks often buy or sell their local currencies using foreign reserves to maintain a fixed exchange rate band against major foreign currencies like the US dollar. When a central bank buys its own currency to stop it from weakening, it pulls local cash out of the banking system, which naturally pushes up local interest rates.