There are trade creation effects and trade diversion effects. The trade creation effect refers to the benefits generated by products from domestic production with higher production costs to the production of customs union countries with lower costs. The trade diversion effect refers to the loss incurred when a product is imported from a non-member country with lower production costs to a member country with a higher cost. This is the price of joining the customs union. When the trade creation effect is greater than the transfer effect, the combined effect of joining the Customs Union on the member countries is net profit, which means an increase in the economic welfare level of the member countries; otherwise, it is a net loss and a decline in the economic welfare level.
