Authorities in Hong Kong have moved in to dampen demand at the highest end of that city's real estate market.

Coming on the heels of a developer there last week setting a world price record for the sale of an apartment -- $9,200 U.S. per square foot -- the Hong Kong Monetary Authority increased the amount of the down payment required from 30% to 40% of the purchase price to buy property valued at U.S. $2.8 million or more.

The Hong Kong Monetary Authority functions as a central bank.

Hong Kong has been immune to much of the world's housing market crash. In fact, quite the opposite has occurred. Home values there have skyrocketed, in part because of low interest rates and buyers from mainland China availing themselves of Beijing's $636 billion U.S. stimulus package. Mainland Chinese now account for as much of 40% of Hong Kong's home purchasers.

At the heart of the record-breaking prices is of course the basic law of supply and demand. The government owns all the land in Hong Kong and releases plots for auction from a pre-approved "application list" after a developer's offer triggers a secret reserve price.

The Hong Kong government denies its policies have created a property price bubble.

In the second quarter of this year, Hong Kong's GDP grew 3.3% yet prices in the so-called luxury sector are reported to have risen 30% since January.