Lael Brainard, a member of the Federal Reserve’s Board of Governors, delivered a speech in 2017 that included this observation: “At a time when the unemployment rate has fallen from 8.2 percent to 4.4 percent, core inflation has undershot our 2 percent target for 58 straight months. In other words, the Phillips curve appears to be flatter today than it was previously.” Briefly explain why the data Brainard cites indicate that the Phillips curve in 2017 was relatively flat.