Finally, besides these clearly identifiable sources of risk, there remains the broader issue that  4  The simplest accelerationist version of the Phillips curve relates the change in inflation to the level of labor market slack; more-complicated versions also highlight the influence of inflation expectations, changes in marginal production costs, and other factors.
Evidence for the United States and other countries that the sensitivity of inflation to resource slack may be nonlinear can be found in André Meier (2010), “Still Minding the Gap – Inflation Dynamics during Episodes of Persistent Large Output Gaps,” IMF Working Paper WP/10/189 (Washington: International Monetary Fund, August).