The article reviews the evolution of the approaches to solving pension security problems in view of demographic challenges. The United States have made the choice of combination the Old-Age, Survivors, and Disability Insurance federal program (OASDI) and the private employer's pension plans (sponsored by the employer or by the worker and his employer), the personal pension accounts. OASDI has been accompanied since the end of the last century by the increasing worker's participation in employer's various pension schemes. While the Government Social Security system provides protection in the form of the guaranteed pensions to retired persons, pension benefits for the participants of voluntary defined contribution plans depend on their personal choice. Although the role of private pensions is growing, the results of a comparative analysis has shown that private pension benefits are mainly complimentary to government pension benefits, especially for low-income persons. It's pointed out that US government policy has become an influential factor of the retirement income sources ' diversification, providing special measures for increasing the availability and motivation of participating in private pension plans and opening personal pension accounts; for regulating the security of pension savings and preventing undue constraints at the same time. The paper also focuses on how American households build up financial assets for preparing themselves for retirement, pointing out that the increasing part of them have savings complimentary to OASDI insurance and employer's pension plans (mainly it means savings and investments one accumulate on his own through stocks, bonds etc.). The strong trend toward voluntary defined-contribution plans (away from defined-benefitplans), personal accounts is the subject to different risks and demands adequate regulation, more information on entitlement. Besides, the access and the participation in employer's retirement plans vary greatly among private industry workers and depend whether they are in the lowest or in the highest wage category, full-time workers or part-time workers, working at the large or at the small firm. Lower-income and part-time workers find it harder to contribute sufficient amount to voluntary schemes, personal accounts; they also might be less prepared for making the decisions concerning investment of their pension resources. Meanwhile, this trend may lead to increasing inequality among future retirees.