Some industries, like the athletic shoe industry, are dominated by a small number of firms with strong brands. These industries are difficult to break into without spending heavily on advertising. The barrier to entry that the firms in these types of industries have erected is referred to as:

Specialization—the division of labor—enhances productivity and efficiency by a) allowing workers to take advantage of existing differences in their abilities and skills. b) avoiding the time loss involved in shifting from one production task to another. c) allowing workers to develop skills by working on one, or a limited number, of tasks. d)all of the means identified in the other answers.