The factor-price equalization theory and transportation costs Which of the following statements about the factor-price equalization theory and the effects of transportation costs are correct? Check all that apply. A. Workers in trading nations always earn the same wages, and capital earns the same interest income. B. Free trade, in the absence of transportation costs or other barriers to trade, tends to equalize product prices and factor prices. C. Differences in transport costs do not affect the comparative advantage of trading nations. D. Transportation costs prevent product prices from equalizing.