Paul Krugman outlines his story of secular stagnation in a blog post this morning. The odd part of the story is that the trade deficit is nowhere in sight. The punchline is that a slower rate of labor force growth should lead to a reduction in demand. The simple arithmetic is that if the rate of labor force growth slows by 1.0 percentage point, then this would be expected to reduce investment by 3.0 percentage points of GDP.
This is a story of a demand gap that could be hard to fill, but how does that compare to a trade deficit that peaked at just shy of 6.0 percent of GDP in 2005 and is still close to 3.0 percent of GDP today? Why are we not supposed to be worried about this cause of a shortfall in demand?
Back in the days before the United States began running persistent trade deficits, the standard theory held that rich countries like the United States should be running trade surpluses. The argument was that capital was plentiful in rich countries, therefore they should be exporting it to poor countries where capital is scarce. This would lead to both a better return on capital and also allow developing countries to grow more rapidly.
We have seen the opposite story in the United States, especially after the run-up in the dollar following the East Asian financial crisis. This has contributed in a big way to the "secular stagnation" problem, but for some reason there continues to be a reluctance to talk about it. (No, being the reserve currency does not mean we have to run a trade deficit.)