In his NYT column on whether the turmoil of Trump's presidency is slowing economic growth, Neil Gross refers to concerns about "secular stagnation" raised by former Treasury Secretary Larry Summers. Secular stagnation just means insufficient demand in the U.S. economy. While the column sees the major cause as weak investment demand, the more obvious cause of secular stagnation is the U.S. trade deficit.
The trade deficit is running at annual rate of more than $540 billion a year, close to 2.8 percent of GDP. This is money that is creating demand in other countries, not the United States. If the trade deficit were suddenly brought to zero it would have the same effect on demand as an increase in annual investment of $540 billion. That is far larger than any shortfall that could be explained by factors Summers cited.
It is bizarre that the trade deficit never features in discussions of secular stagnation since it is obviously a major drain on demand in the U.S. economy. It also runs contrary to textbook economics which holds that rich countries like the United States should be capital exporters to the developing world, which means that we should be running large trade surpluses, not deficits.
But, as the saying goes, economists are not very good at economics.