President Obama pronounced yesterday "a historic day, a watershed event," because doctors, hospitals, drug makers and insurance companies voluntarily offered $2 trillion in cost reductions over 10 years. But if history is a guide, their commitments may not produce the promised savings, according to this analysis from the New York Times. Their proposals are vague, and none of the savings are guaranteed, the analysis states. Without such a guarantee, budget rules would normally prevent Congress from using the savings to pay for new initiatives to cover the uninsured.