幾個對貨幣政策有興趣的朋友要求我解讀一下美聯儲局2月10日在國會的聲明和上週加貼現率的行動。其實，各位如果仔細閱讀2月10曰的聲明，包括裏面的9個附錄，便不難了解美聯儲局的動机。
信貸寬鬆政策，和其地支持金融体系的持殊措施，已令流動資金充斥市場，遠超存款準備金規定所需，剩餘的準備金，超過一万億美元。在這情況下，聯儲局是很難用聯邦基金指標利率作為貨幣政策利率的，因為要在聯邦基金市場上成功維持指標水平，而指標水平是高於零的話，市場上一定要有缺乏資金的狀況，而不是水浸的狀況。簡單說，水浸已令聯邦基金指標利率失去實行貨幣政策的功能，有需要暫時利用其他能有效控制基礎貨幣价格〔即利率水平〕的工具。
美聯儲局的意向，在聲明中可清楚見到，是利用利率走廊〔好像香港以前的「流動資金調節机制」LAF一樣〕，上限是貼現率，下限是聯儲局最近引入的剩餘準備金利率。經上週調整貼現率後，上限是0.75%，下限是0.25%，有50點子的走廊空間。往後如有需要調高利率，我相信聯儲局會將下限和上限一齊調高〔或只調高下限，即剩餘準備金利率〕，而聯邦基金指標利率的角色會暫時被淡化。
這是一個不常見的美國貨幣政策操作模式的結構性轉變，具深遠影響。應繼續留意發展，特別是聯儲局主席本週的發言。
任志剛
A few friends with a keen interest in monetary policy asked me to provide an interpretation of the Statement of the Fed of 10 February before the US Committee on Financial Services and the subsequent hike in the US Discount Rate. I thought that the messages are quite clear from the Statement, which we all should read carefully, including its 9 footnotes.
Credit easing and other temporary support measures for the financial system have meant that the money market is flooded with liquidity. Excess reserves are now over US$1 trillion. Technically, to hit a positive interest rate target, determined by the Fed Funds Target Rate, there is a need for shortage in the money market. As it is now, the condition in the money market makes the Fed Funds Target Rate unworkable as the policy interest rate and there is a need for an alternative tool.
The intention of the Fed, as articulated quite clearly in the Statement, is to use an interest rate corridor (something similar to the Liquidity Adjustment Facility used in Hong Kong in the past before formalizing the Discount Window), with the Discount Rate as the upper limit and the Interest on Excess Reserves introduced recently as the lower limit. With the hike in the Discount Rate last week, the upper limit of the corridor is 0.75% and the lower limit is 0.25%, giving a corridor of 50 basis points. Later on, if there is a need for higher interest rates, I believe that the Fed will shift the corridor upwards by changing both the upper and lower limits, or just increase the lower limit (the Interest on Excess Reserves), in which case the height of the corridor would narrow. The role of the Fed Fund Target Rate will be correspondingly, and perhaps temporarily, diminished.
This is a structural change in the monetary policy operation model of the Fed, which does not occur very often and may have important implications. This is something to be watched closely from now on (if not already), starting with whatever that Chairman Bernanke has to say this week.
Joseph Yam
Joseph Yam's Blog 