
The Medicare Modernization Act (MMA) set minimum federal standards for prescription drug coverage. Plans wanting to participate in the program could offer the standard benefit or a variation that was approved as actuarially equivalent by CMS. Most plans elected to modify the standard design with their own formularies and combination of enhanced benefits. Each plan sought the right combination of premium level, benefit package, formulary structure, and tiered co-pays that they believed would attract and keep an acceptable share of the market while generating a profit to the plan.