The 2010 report takes data from 2008 and compares 141 countries by measuring the degree to which a country's policies and institutions support economic freedom.
New Zealand (8.27) has retained its third place behind Hong Kong (9.05) in first place and Singapore (8.70) in second place.
Zimbabwe (3.57) is at the bottom of the economic scale, where it is closely ranked by Myanmar, Angola and Venezuela.
Focal points for the survey are the size of government, judicial system and security of property rights. Access to sound money, freedom to trade internationally and regulation of credit, labour and business are also considered.
The global recession has seen the average world rating of economic freedom drop for the first time in decades, said the think-tank. An average rating of 6.67 in 2008 had fallen from 6.74 in 2007.
However, the report notes that countries that have free and open markets also tend to have a strikingly higher quality of life.
People living in countries of greater economic freedom appear to enjoy higher levels of economic well-being, greater individual freedom and longer life expectancy.
Decreased unemployment levels and fewer homicides also seem to accompany higher levels of economic freedom.
