Opponents of NAFTA argue that the operation of the treaty has harmed various sectors of the economies of both Mexico and the United States. They argue that the agreement has had the effect of suppressing wages in the US. This is because the agreement makes it easier for firms to move their operations outside the country if wages increase in the US. Opponents also argue that the agreement has hurt workers and farmers in Mexico. It is said to lead the to the creation of the maquiladoras in which Mexican workers for low wages in bad conditions. It is also said to have destroyed the livelihoods of Mexican farmers who cannot compete with the more mechanized and organized farms in the United States.
This is, of course, only one side of the story. Many would argue that the agreement has been beneficial. But many critics of NAFTA argue that it has had these and other negative effects.