Why protectionism spells trouble for global economic growth

It is sometimes alleged that for all the microeconomic distortions that protectionist policies inflict, there can be a silver lining in terms of macroeconomic gains: more jobs, more output and a stronger trade balance. Indeed, some economies today are seemingly using commercial policy to pursue macroeconomic objectives. Tariffs can dampen imports, boost net exports (the difference between exports and imports, or the trade balance), and so boost GDP, other things being equal.