... entry in their rivals' home markets than the barriers to entry of foreign firms in US markets. US firms are at or near the forefront in technological advances, especially in computers and in medical, aerospace, and military equipment, although their advantage has narrowed since the end of World War II. The onrush of technology largely explains the gradual development of a "two-tier labor market" in which those at the bottom lack the education and the professional/technical ... — The 2002 CIA World Factbook • US Government