As the fiscal cliff talks evolve and devolve, the latest spat has been whether the arc of federal spending should be curtailed by changing the way that we assess costs. The proposal from the White House is to switch the way cost-of-living adjustments are made for Social Security benefits. Rather than pegging those to the Consumer Price Index as currently calculated, these would be pegged to a “chain-weighted” Consumer Price Index, which would save as much as $125 billion in additional benefits over the next decade.