The query is emerging as the ultimate challenge in reining in healthcare costs that now consume $2.5 trillion per year, or 16% of the economy: How will tough decisions be made about what to spend money on? The question permeates all levels of medicine, according to the Washington Post: the use of tests that many argue are unnecessary; how early to intervene with common conditions such as heart disease and prostate cancer; how aggressively to treat patients nearing their life's end.