And just like... Federal Reserve Chair confirms the Twin Secular Stagnation Hypotheses in one paragraph of his speech:
Per Powell, "the U.S. economy faces a number of longer-term structural challenges ... For example, real wages, particularly for medium- and low-income workers, have grown quite slowly in recent decades. Economic mobility in the United States has declined and is now lower than in most other advanced economies.2 Addressing the federal budget deficit, which has long been on an unsustainable path, becomes increasingly important as a larger share of the population retires. Finally, it is difficult to say when or whether the economy will break out of its low-productivity mode of the past decade or more, as it must if incomes are to rise meaningfully over time."
For those who might want to read about an even more fundamental (and causally linked to the Powell's challenges) structural decline in the Cayman Financial Review here: http://trueeconomics.blogspot.com/2018/08/18818-monpolization-trends-in-advanced.html.
What is note worthy in Powell's passage is the words "in recent decades". Powell is correct (and I pointed this fact out on a number of occasions) that the adverse trends in the U.S. economy have been present for much longer than the post-Global Financial Crisis shocks residual effects. The economic stagnation (expressed in the abysmally low growth rates of economic prosperity for the lower 90 percent of the American population; in woefully slow expansion in productivity, compared to historical trends; in structurally less competitive nature of the economy and growing monopolization and oligopolization of the U.S. markets; in reduced physical and social mobility; in falling pensions savings provisions for the majority of the U.S. population; and so on) has pre-dated the GFC and its roots rest much deeper than the financial disruption of the 2007-2010 crisis.