By John S. McClenahen Hong Kong, a special administrative area of the People's Republic of China, repeats in 2001 as the freest of 156 economies ranked by the Washington-based Heritage Foundation and the Wall Street Journal. Singapore is listed as No. 2 and New Zealand is No. 3 in the ranking, which is known formally as the Index of Economic Freedom and based on 50 economic variables grouped into 10 categories ranging from banking and finance to black-market activity. The U.S. ties for No. 4 in the ranking, along with Estonia, Ireland, Luxembourg and the Netherlands. The least-free economies surveyed are North Korea, Iraq, Libya, Cuba, Laos and Iran. Overall, economic freedom has advanced in the world during the past year, the survey claims, with 73 of the 156 rated nations granting more economic liberty, while 53 imposed new restrictions.