That central banks should hold foreign currency reserves is a key tenet of the post–Bretton Woods international financial order. But recent growth in the reserve balances of industrialized countries raises questions about what level and composition of reserves are “right” for these countries. A look at the rationale for reserves and the reserve practices of select countries suggests that large balances may not be needed to maintain an effective exchange rate policy over the medium and long term. Moreover, countries may incur an opportunity cost by holding funds in currency and asset portfolios that, while highly liquid, produce relatively low rates of return.
And this, from the opening paragraph, is also worth drawing attention to:
To date, the foreign exchange reserves of major industrialized economies have received relatively little attention in public policy circles, with few questions posed regarding their optimal size, composition, and use. Instead, discussion of foreign exchange reserves tends to center on the large holdings of emerging market countries—including China, whose reserves reached about $3 trillion in mid-2012. Foreign currency reserves are also overshadowed in public discussion by the much larger external imbalances that countries amass in the form of trade deficits and surpluses.
The key element here is that this paper only looks at the US, the UK, Switzerland, Japan, Canada, and the euro area, and rightly so as these are the big fish of the global FX market. The brief mention of emerging market countries’ holdings highlights what’s implied in the debate but rarely stated explicitly, so allow me to do so now: