Medicare Part D is the prescription drug program that provides 27 million American seniors with affordable prescription medications. A successful program with a 90% satisfaction rate, Part D also manages to cost 41% less than originally anticipated, says the Congressional Budget Office. How is that possible? Here's a closer look.

Medicare Part D uses a competitive, free market model to keep costs low. Through direct negotiations with pharmaceutical companies, insurance companies compete with each other over the cost of prescription medications. Thus, Medicare beneficiaries are able to choose from a wide range of drug benefit plans and select the plan that best suits their needs and their budget.

These negotiations have a direct impact on beneficiaries' pockets. When Medicare Part D began in 2006, the government estimated that 2011 average monthly premium would be $52. Instead, it was $30, and is expected to stay the same through 2013.

A competitive marketplace for Part D plans enables seniors to have affordable access to the prescription drugs they need without increasing their out-of-pocket health care costs. As we look ahead to 2013, we'll be looking out for policy proposals that could jeopardize Part D's success by increasing drug costs and reducing access to medicines for older Americans. Sign up for our email list to learn how you can take part.