The Secret Source of Economic Weakness: The Trade Deficit

I know, it isn't really secret. The Commerce Department publishes data on the trade deficit every month, but given the extent to which it is ignored in economic policy discussions, as for example in this otherwise thoughtful NYT column, it might just as well be secret. 

The basic story is incredibly simple. If we are buying more from abroad than we are selling, this means that we have negative national saving. If we have negative national saving, then either the public sector must have...