It occurs when traded commodity is shifted from the highest cost domestic producer to the lowest cost customs union member country.

It is an international organization that deals with the rules of the multilateral
trading system.

It emanates at the formation of the customs unionw hich represents very short run effects.

It occurs when traded commodity is shifted from the lowest cost country that is out of the customs union to the relatively higher cost customs union member country.

It constitutes the area in between the demand and the price of the commodity that is subject to examination.