The challenge of the 21st century: innovating and adapting Social Security systems to economic, social, and demographic changes in the English-speaking Americans.

The Social Security Programs in the United States are complex and have evolved over a long span of years. However, it is possible to categorize much of this experience into two different eras in which Social Security functioned in a distinctive environment, and a third era that is now beginning. The middle third of this century was an "age of invention," in which the programs grew rapidly under favorable social and economic conditions. Since then, the programs have experienced an "age of accommodation," in which growing financial constraints have permitted only limited changes in the program. We can look forward to an "age of maturation" in the decades to come, as most persons reaching retirement will have been covered by Social Security during their entire working careers. The declining ratio of workers to beneficiaries and a wide range of demographic and social changes will present significant challenges. The Social Security programs must change considerably to respond to the demands of a new era, and vigorous efforts to do so are underway.