To the Editor.
—Unfortunately, the simulation study of MSAs conducted by Dr Keeler and colleagues1 did not simulate the conditions under which MSAs would be offered to employees by their companies. Rather, the simulations assumed that everyone in the United States would be offered a choice between 3 identical plans: a typical 1996 FFS policy, a typical staffmodel health maintenance organization (HMO), and an MSA.In reality, companies will carefully tailor their benefit options to achieve at least 2 objectives. First, they will design the options to control adverse selection among them. Second, they will not alter their benefit options and include an MSA unless their benefit costs are reduced or stay the same. This means that each company's set of options will differ in some or many respects from those of others because they will be tailored to the risks and preferences of each company's workforce; many more options than the 3