The role of international trade was irreplaceable at the start of the COVID-19 pandemic crisis, especially the trade in medical supplies and food for all affected countries. Trade as a part of this crisis, certainly should not be an element of further countries' closing and new trade barriers...

Welfare with the maximum-revenue tariff is compared to free-trade welfare under perfect competition in the case of a large country able to affect its terms of trade; under Cournot duopoly with differentiated products; and under Bertrand duopoly with differentiated products. Under perfect...