The actually useful and important chart from Yellen’s speech is this one:
Though it is accompanied by a head-scratching bit of astrology, stable nominal income expectations are extremely important to a stable macroeconomic environment. What you see from the chart above is exactly what you see in the famous NGDP chart; a central bank that let actual and expected nominal income crater, and then resume growth from the new, lower level. No catch-up at all. There is no great mystery to the slow nominal growth post-Great Recession. We need to stop pretending that there is.