New Delhi, March 17 -- Is there a method to the madness that seems to guide US trade policy under President Donald Trump? An effort to revive American manufacturing behind import tariff walls, some aver, can be followed by a tax on capital inflows.

The argument is that the US dollar's external value is kept unnaturally high by demand from trade partners buying Treasury bonds to stuff their forex reserves; a levy on bond purchases (or payments) could act as a disincentive.

This move to weaken the dollar, aimed at making US exports more competitive, may be backed by a sovereign wealth fund that buys foreign assets to balance capital inflows with outflows. Also, by a "Mar-a-Lago Accord" that gets other nations not to depress their own curr...