Brian Snyder/ReutersEconomists and top Federal Reserve officials often admit to being puzzled by low inflation and stagnant US incomes, even in the face of a rapidly falling unemployment rate that, at 4.4% in April, is close to its historic lows. Here’s Fed Board Governor Lael Brainard in a May 30 speech: "There is little indication of an outbreak of inflation — rather, the latest data on inflation have been lower than expected.