 This phenomenon can be mainly attributed to poverty in Mexico, the growing demand for unskilled labor in the U.S., the existence of established family and community networks that allow migrants to arrive in the U.S. with people known to them.The framework of U.S. immigration law has largely remained the same since 1965.The U.S. economy needs both high-skilled and low-skilled immigrant workers to remain competitive and to have enough workers who continue to pay into Social Security and Medicare as the U.S. population grows older.