In the long run a perfect competitor's output is _________ equal to its most efficient output.

To think at the margin means to consider

A) how people behave in their own self-interest. B) how a small change in one variable affects another variable. C) how people will decide what to purchase. D) how nothing remains constant over time.

The Social Security retirement program is financed by a 10.6 percent payroll tax that applies to earnings up to an income cutoff that is adjusted upward annually by the growth rate of nominal wages. As of 2013, the income cutoff was

a. $15,000. b. $32,700. c. $113,700. d. $250,000.