Planes are seen under construction at a Boeing assembly plant LUC OLINGA/AFP/Getty Images

The Dark Matter of Trade

Donald Trump has argued that trade wars are easily won by the country with the deficit, because the other party has more to lose. But just as trade has moved from goods to services and on to knowledge, so may trade wars, with a tariff on steel answered by a tax on Amazon or Google.

CAMBRIDGE – If you are flying a plane, it is useful to know how to keep it level. To do so, you must be able to read the instruments. If the plane is flying level, but you think it is heading down, you may pull back on the yoke and put the plane into a stall. This is what may be happening today with US trade policy.