The editors of The New York Times write: “Unlike the gauge of inflation currently in use, the chained index captures the ability of consumers to adjust their spending across categories as relative prices change — for instance, spending less on fuel as gas prices go up and more on groceries as food prices go down. Such substitution causes the chained C.P.I. to rise more slowly than the current measure, which would result in a lower annual COLA and huge budget savings. The move to a chained C.P.I. would reduce benefits by some $135 billion over 10 years, and far more in later decades because of compounding.”