Final answer:
When countries shift production toward their areas of comparative advantage, their combined production of both goods rises.
Step-by-step explanation:
When countries shift production toward their areas of comparative advantage, their combined production of both goods rises. In the given scenario, the United States transfers labor toward producing refrigerators, resulting in a decrease in shoe production but an increase in refrigerator production. Meanwhile, Mexico transfers labor toward producing shoes, causing a decrease in refrigerator production but an increase in shoe production. This demonstrates the benefits of specialization and trade, as both countries can produce more of both goods by focusing on what they are relatively better at.