Allowing for known measurement biases, these inflation indexes have been in a neighborhood that corresponds to effective price stability--a long-held goal assigned to the Federal Reserve by the Congress. But we can pause at this achievement only for a moment, mindful that we face new challenges in maintaining price stability, specifically to prevent inflation from falling too low. This is one reason the FOMC has adopted a quite accommodative stance of policy. A very low inflation rate increases the risk that an adverse shock to the economy would be more difficult to counter effectively. Indeed, there is an especially pernicious, albeit remote, scenario in which inflation turns negative against a backdrop of weak aggregate demand, engendering a corrosive deflationary spiral.