Sweden was the fifth-ranked country in the index, followed by Canada, Norway, Britain, Ireland and Malaysia.
Australia was ranked 15th, in between Iceland and Denmark, while the United States was ranked 18th.
Guinea, in West Africa, was the lowest-ranked country, ahead of Burundi, Angola, Haiti and Benin.
Other research, however, tells a different story about this country.
It emerged last year that New Zealand had slipped from 73rd to 146th on a United Nations ranking of prospective countries to invest in over the past decade.
Local think tank the New Zealand Initiative blamed overly restrictive entry regulations, which include a need for investors to become residents.
The relatively low economic fundamentals score this country received from the Milken Institute is likely to have been influenced by strict entry regulations.