Tariffs are like taxes for goods being imported into a country from another. They are meant to limit or slow imports of certain goods to either protect national industries or decrease competition from the goods being imported. It decreases trade and slows economic business. For example if Japan imports one million cars into the USA then sales of USA Auto makers will decrease. If tariffs limit the importation then USA auto makers have more ability to sell cars through less competition. Unless the tariffs are paid and if so then this can be used for government expenditures like subsidies to Assist Auto makers. Or the end result can be tariffs put up from Japan for their goods from the USA to limit our exports. It might be cause a decrease overall to all exports for the nation putting up the tariffs. This is what happened after WW1 when the war ended production was high to supply goods for the war. When the war ended the demand ended then the world had a surplus of goods. To protect industries nations put up tariffs to protect national interest. THis caused others to follow suit. THen the worlds trade slowed nations that depended on trade could not sell goods. Their economies suffered. People were put out of work. And this had a domino effect because no jobs meant very little spending inflation increased to make up for loss of sales and the world was plunged into a Depression. It took a new world war to bring the world out of it. And the New Deal policies of FDR. Tariffs are a bad idea during economic slowdowns because it decreases trade.