Changes in supply and demand in the labor market will cause changes in wages

All of the following would increase the natural rate of unemployment EXCEPT

A) union activity restricts the mobility of labor. B) government licensing of teachers restricts employment. C) a mismatch of skills and jobs. D) a downturn in the economy.

Data concerning the four-firm concentration ratios for U.S. manufacturing industries indicate that

a. very few oligopolies exist in the real world but the oligopoly model is still useful because it tells us something about firm behavior b. oligopolies are the second most prevalent market structure, monopoly being the first c. the four leading firms usually have less than 10 percent of industry sales d. the ratios are considerably less than the ratios in Canada and Western Europe e. oligopolies are very common