Shanghai is a case in point here. Average daily turnover on the Shanghai stock exchange may have hit US$17 billion in the first half of this year - more than three times the turnover of the Hong Kong market - but foreign participation was negligible. According to Goldman Sachs, foreign investors own only 0.5 per cent of the A share market's capitalisation, which hardly qualifies Shanghai as an international centre. In contrast, overseas investors own between 30 and 50 per cent of many major Hong Kong-listed stocks.

But to get a better idea of how international a financial centre it really is, it makes sense to look at the level of activity in its foreign exchange market. After all, most international business involves a currency transaction at some point, so if international deals are being struck, they will show up in the foreign exchange data.

And when we do look, it becomes clear that far from declining, Hong Kong is actually gaining ground as an international centre.

According to the results of the Bank for International Settlements' triennial foreign exchange market survey released yesterday, in April this year currency turnover in Hong Kong averaged a thumping US$237.6 billion a day.

That makes Hong Kong the sixth biggest foreign exchange trading centre in the world (see the first chart below). What's more, Hong Kong is growing fast and capturing market share from other cities in the Asian time zone. While Japan and Singapore have both seen their share of the world market decline since 1998, Hong Kong's has increased from 3.8 to 4.7 per cent (see the second chart).

In contrast, the mainland's share of the global foreign exchange market remains tiny. Turnover in April was just US$19.8 billion a day, putting the mainland in 22nd place on the global league table of foreign exchange centres, behind Norway and with less than a tenth of Hong Kong's turnover.

Similarly, Hong Kong dwarfs the mainland when it comes to dealing in interest rate derivatives. Every day Hong Kong trades swaps, options, forward rate agreements and other exotica worth US$18.5 billion. The mainland manages just US$1.5 billion.

And just as Hong Kong's position as a centre for foreign exchange and derivatives trading remains unthreatened by Shanghai, there is little sign that the US dollar is going to be knocked off its perch just yet by the yuan or any other currency.

According to the BIS survey, the US dollar is still traded in a massive 85 per cent of all currency transactions. That level has barely changed from three years ago, despite the financial world's supposed loss of faith in the currency (see the third chart).

Meanwhile, the yuan figures in just 0.06 per cent of currency trades, less than half as many as the Colombian peso. Moreover, according to the BIS data, the yuan's importance in the global foreign exchange market has actually declined since 1998, when it was traded in 0.08 per cent of all transactions.

Sure China's importance as a trading nation and Beijing's efforts to denominate more of its trade flows in yuan mean that the Chinese currency is likely to gain some ground between now and the next BIS survey in 2013.

But that gain will be small. The reason is simple: no matter how important China is as a trading economy, world trade flows are small compared with financial flows. And the unsurpassed depth of US financial markets means those financial flows will continue to be denominated overwhelmingly in US dollars.

As a result, the US dollar's position as the world's premier currency looks secure for the foreseeable future - just like Hong Kong's position as China's only significant international financial centre.