Foreign currency reserves

Reserve assets held by a country's monetary authorities (government and central bank) in preparation for official external payments or to intervene in the foreign exchange market to stabilize exchange rates. Specifically, they consist of (1) monetary gold, (2) foreign currency-denominated cash and securities, (3) SDRs (Special Drawing Rights of the International Monetary Fund, abbreviated as IMF), and (4) reserve positions that can be withdrawn unconditionally from the IMF. In Japan, they are held by the Ministry of Finance (Foreign Exchange Fund Special Account) and the Bank of Japan, and most of the $1.024 trillion (as of the end of May 2009) is managed short-term as U.S. Treasury bills (TBs) and dollar deposits.

Under a fixed exchange rate system, monetary authorities must intervene in the market to maintain the exchange rate in the event of a surplus or shortage in the supply and demand of foreign currency in the foreign exchange market caused by an imbalance in the balance of payments. If the balance of payments is in surplus and there is an excess supply of foreign currency, foreign exchange reserves will increase as they intervene to buy, and conversely, if the balance of payments is in deficit and there is an excess demand for foreign currency, foreign exchange reserves will decrease as they intervene to sell. In order to maintain a fixed exchange rate system, a certain amount of foreign exchange reserves must be held in preparation for this balance of payments deficit.

In contrast, in the case of a floating exchange rate system, the surplus or shortage of foreign currency supply in the foreign exchange market caused by an imbalance in the balance of payments is automatically adjusted by fluctuations in the exchange rate, so in principle there is no need for foreign currency reserves for market intervention. However, in reality, a completely freely floating exchange rate system is not in place, and market intervention is necessary to suppress fluctuations in the exchange rate, so foreign currency reserves are necessary.

Even among countries with a balance of payments surplus, those with a system close to a freely floating exchange rate system, such as Japan, have only seen a slight increase in their foreign exchange reserves due to investment gains on the reserves, except for when purchases are made during temporary, dramatic fluctuations in the exchange rate. In contrast, China, which has an exchange rate policy fixed to the US dollar, has seen an almost linear increase in its foreign exchange reserves, overtaking Japan in February 2006 to become the country with the largest foreign exchange reserves in the world, with a balance of $2.1316 trillion as of the end of June 2009.

There is no clear standard for how much foreign exchange reserve is appropriate to hold. This is because it depends on the country's exchange rate system, balance of payments structure, foreign currency procurement capacity, etc. However, in recent years, foreign exchange reserves have been accumulating, mainly in Asian countries, behind the huge current balance of payments deficit of the United States. In this context, there has been a movement to seek more efficient management of foreign exchange reserves, and it is noteworthy that signs of currency diversification have begun to appear, such as a conversion from dollars to euros and the IMF's purchase of SDR-denominated bonds due to growing concerns about the dollar.

[Seiichi Nakajo]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

一国の通貨当局（政府および中央銀行）が、公的な対外支払いに備えたり、為替(かわせ)相場の安定を図る目的で外国為替市場に介入するために保有している準備資産。具体的内容は、(1)貨幣用金、(2)外貨建て現預金および有価証券、(3)SDR（国際通貨基金、略称IMFの特別引出権）、(4)IMFから無条件で引き出せるリザーブ・ポジション、からなっている。日本では、財務省（外国為替資金特別会計）と日本銀行が保有しており、1兆0240億ドル（2009年5月末現在）の多くがアメリカ財務省証券（TB）やドル預金として短期運用されている。

　固定為替相場制の下では、国際収支の不均衡による外国為替市場の外貨需給の過不足に対して、通貨当局は為替相場の維持のために必ず市場介入をしなければならない。国際収支が黒字で外貨の超過供給であれば、買い介入するため外貨準備は増加し、逆に国際収支が赤字で外貨の超過需要であれば、売り介入をするため外貨準備は減少する。固定為替相場制の維持のためには、この国際収支赤字に備えて、一定の外貨準備を保有しなければならない。

　これに対して、変動為替相場制の場合は、国際収支の不均衡による外国為替市場の外貨需給の過不足は、為替相場の変動によって自動的に調整されるため、原則としては市場介入のための外貨準備は不必要となる。しかし、現実には完全に自由な変動為替相場制ではなく、為替相場の乱高下を抑えるために市場介入をしなければならないため、外貨準備が必要となっている。

　国際収支の黒字国でも、日本のように自由変動為替相場制に近い制度をとっている国では、一時的な為替相場の激変時に買い介入をして外貨準備が増加する以外は、外貨準備の運用益による微増にとどまっている。これに対して、米ドルに固定的な為替政策をとっている中国では、ほぼ直線的な外貨準備の増加が続いており、2006年2月に日本を抜いて世界一の外貨準備保有国に躍り出るとともに、2009年6月末には2兆1316億ドルもの残高を有している。

　どの程度の外貨準備を保有することが適正かという明確な基準はない。それは、その国の為替相場制度、国際収支構造、外貨の調達能力などによって、異なるからである。しかし、近年はアメリカの巨額な国際収支赤字の裏側で、アジア各国を中心に外貨準備が累増している。そうしたなかでは、外貨準備のより効率的な運用を模索する動きが顕在化するとともに、ドル不安への懸念の高まりによって、ドル建てからユーロ建てへの転換、IMFのSDR建て債券購入など、通貨の分散化の兆しが出始めたことが注目される。

［中條誠一］

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