As is well known, United States Fed Reserve chairman Ben Bernanke announced a third round of quantitative easing (QE3) in September, and then the Hong Kong dollar did exactly what it has done the two previous rounds of QE: trade at the bottom of its band against the US dollar at HK$7.75.
So far it's unclear whether this is due to money coming from offshore, or because funds holding foreign currency in Hong Kong have decided to buy investments such as stocks and property.
In any case, lots of people are buying Hong Kong dollars in preparation to buy Hong Kong assets, creating appreciation pressure on the local currency.
Two weeks ago the Monetary Authority traded HK$14.4 billion for foreign currencies, effectively weakening the local dollar. It was the authority's first such intervention in two and a half years.
This was remarkable in itself but it also flagged up the possibility that Hong Kong was riding a liquidity bubble. After all, previous rounds of QE drove prices up for local stocks and property, in 2009 and 2010.
According to market-data provider EPFR, aggregate net inflows from overseas-domiciled funds into Hong Kong rose more than US$400 million since early September. This reflects investors' appetite for investments in the local currency.