Hong Kong has been named the world's ‘freest’ economy for the eighth consecutive year in a recent survey, but its lead over rival Singapore has narrowed due to new data being used for assessing the size of the black market.

The 2002 Index of Economic Freedom from the Heritage Foundation looks at levels of regulation, corruption and the extent of the informal economy to assess how open a country’s markets are. The survey gave Hong Kong a score of 1.35 and Singapore 1.55. Scores range from one to five with a lower number indicating a freer economy.

Hong Kong took first place because of its duty-free ports, open markets and low level of regulation, according to the Heritage Foundation. Singapore's score was unchanged from last year but Hong Kong's slipped from 1.3 because of the size of the black market.

Different data was used this year to assess the size of the black market, which also affected the scores of other economies. "Basically, it was a one-time adjustment which happened to a number of countries as we transferred our database from our own internal compilation in this one category into the global [Transparency International] database," Heritage Foundation president Edwin Feulner said.