President Bush continues to make a case for restructuring Social Security, a main plank of his State of the Union address Wednesday. But dissenters are pointing out that the federal program represents only one spending-related problem associated with the exploding elderly population in coming years.

In just 10 years, spending on the elderly will total nearly $1.8 trillion, almost half the federal budget, according to new Brookings Institution and Congressional Budget Office projections. That is up from 29% in 1990 and 35% in 2000.

Medicare and Medicaid compose the majority of that growth is spending. Their combined costs are projected to more than double, to a combined total of $1.2 trillion in 2015, from $473 billion last year. Social Security spending is expected to rise to $888 billion, from $492 billion in that span.

In his proposal to reform Social Security, Bush suggests that younger workers divert up to 4% of income subject to Social Security taxes into individual investments accounts. He said in his State of the Union address that Social Security could be bankrupt by 2042.