THE most important domestic issue facing the U.S. government is how to finance the future pension and health benefits of an aging population.  This problem is important in itself. But it takes on even greater significance because a failure to achieve an appropriate reform of the existing system of financing the programs for the aged would have very serious effects on the entire economy.  In addition, the budgetary consequences of inadequate reform would undermine the government’s ability to deal with all other domestic and international problems.