Wages in the United States and other industrially advanced countries tend to be

Wages in the United States and other industrially advanced countries tend to be higher than wages for similar jobs in less developed countries.There are many economic factors that lead to lower wage rates in underdeveloped countries compared to wage rates in the United States and other industrially advanced countries? What are some of theseeconomicfactors? Why do they lead to lower wages in the less developed countries?Labor unions did not really develop in the U.S. until the 1930s. Why?At this point in time labor unions have not become a factor in determining wages in less developed countries. Why?