The Chinese yuan, also known as the renminbi, is already convertible under the current account - the broadest measure of trade in goods and services. However, the capital account, which covers portfolio investment and borrowing, is still closely managed by Beijing because of worries about abrupt capital flows.
Yuan rise puts heat on Hong Kong dollar peg
With the rising use of the yuan in trade and investment, debate about the Hong Kong dollar's 30-year-old peg to the US dollar is intensifying.
The debate was further fuelled earlier this month when the Bank for International Settlements said that dealing in the mainland currency had reached the equivalent of US$118 billion a day, accounting for 2.2 per cent of the global foreign-exchange market and exceeding the Hong Kong dollar's 1.4 per cent share. That came just three years after Beijing relaxed rules and allowed the yuan to trade in Hong Kong.
Might Hong Kong choose to peg its dollar to the yuan one day? Economists say that's not impossible, but only when the US dollar loses its status as the unrivalled international reserve currency to the yuan - which would take many, many years to achieve.
"The Hong Kong dollar should not be pegged to the renminbi as long as the renminbi is not fully convertible - for example, until China has abolished all capital controls, external and domestic," said Invesco chief economist John Greenwood, known as the "father of the Hong Kong-US dollar peg".
"In my view this will take many years to achieve because one of the essential preconditions for external convertibility is full domestic capital market liberalisation, which itself will take many years to achieve. Don't underestimate how long this would take."
The Hong Kong dollar has been pegged to the US dollar since October 1983, after a monetary crisis triggered a 15 per cent slump in the local currency in one and a half working days. It has been fixed ever since at a rate of around 7.8 to the US dollar. The peg served the special administrative region well during the Asian financial crisis in the late 90s, the severe acute respiratory syndrome outbreak in 2003 and the collapse of investment bank Lehman Brothers in 2008.
However, a number of big names have called in recent years for the peg to be reviewed and consideration given to linking the currency to the yuan instead. They have included the former head of the Hong Kong Monetary Authority, Joseph Yam Chi-kwong, and, most recently, HSBC's Asia-Pacific chief executive Peter Wong Tung-shun.
Wong told a forum in Hong Kong this month that the Hong Kong dollar's international impact would be reduced once the yuan became a global currency and the government should reconsider changing its currency peg system.
Yam challenged the current system in an essay last year.
"No doubt the LERS [Linked Exchange Rate System] has, for almost 30 years of its existence, been a pillar of stability for Hong Kong. But, realistically there are costs involved," Yam wrote.
"There is little or no scope to … control the price or supply of base money to achieve … low inflation, low unemployment and stable and sustainable economic growth."
Some have blamed the dollar peg for Hong Kong's surging property prices amid quantitative easing in the United States. But Greenwood said Hong Kong regulators had protected Hong Kong by limiting leverage, such as by tightening loan-to-value ratios for mortgages, so that when interest rates increased, Hongkongers would be less vulnerable than if they had been accumulating excessive debt.
Meanwhile, a slew of numbers has kept market watchers excited about the yuan's future. It now accounts for 15 per cent of the mainland's global trade and is in the top 10 of world payment currencies. But in reality, economists said, the yuan is still far from being a global currency.
The yuan's market share in global payments is less than 1 per cent, despite a surge in recent usage, according to Swift data. It is not even a member of the Special Drawing Rights basket of the International Monetary Fund.
The basket now uses four key international currencies: the US dollar, euro, British pound and Japanese yen to supplement member countries' official reserves and bolster liquidity.
More importantly, with limited freedom in its interest and exchange rate regimes, the mainland has a highly restricted capital account system, limiting capital flow in and out.
"If China succeeded in abolishing interest rate and other controls in the domestic money and credit markets, then China could proceed to full external convertibility," Greenwood said.