http://www.ssa.gov/policy/docs/ssb/v59n3/v59n3p45.pdf
11 page pdf found at the link. Summary follows here:
In 1924, Chile was the first country in the Western Hemisphere to establish a comprehensive social security program that provided coverage for old-age, survivors, and disability benefits (similar to the present OASDI system in the United States), and cash sickness and medical benefits. By the late 1970’s, it had become clear that massive government subsidies would be needed to continue to pay benefits. Then, in 198 1, Chile became the first country to change from a pay-as- you-go system to mandatory private savings for retirement. As many countries worldwide are currently facing problems with financing their social security systems, they are looking to the experience of other countries to find solutions. The Chilean model has become a popular one to observe. This article provides a description of the problems of the old public system, the transition provisions, the privatized system and its performance to date, and what the United States can learn from the Chilean experience.