Because this term equals the change in relative energy prices multiplied by the share of energy in aggregate output, energy price effects on inflation appear to have fallen by more than can 5 be accounted for by the greater energy efficiency of the economy.
In contrast, unpublished empirical work by the staff at the Federal Reserve Board suggests that, once we take the rising share of imports into account, the influence of import prices on core inflation in the United States has not changed much in the context of reduced-form forecasting models.