The main point of our op-ed, as well as our earlier work, is that most of the increase in per-capita output that occurred after 1933 was due to higher productivity – not higher labor input. The figure [at the link] shows total hours worked per adult for the 1930s. There is little recovery in labor, as hours are about 27 percent down in 1933 relative to 1929, and remain about 21 percent down in 1939. But increasing aggregate demand is supposed to increase output by increasing labor, not by increasing productivity, which is typically considered to be outside the scope of short-run spending/monetary policies.
There is more at the link.