Which of the following macroeconomic variables does not vary much over the seasons?

Which of the following is correct? a. U.S. International trade represents about 50 percent of U.S. GDP

b. Less than 5 percent of world output is sold in a country different from the one in which it is produced. c. Without tariff protection the number of jobs available to domestic workers would decline. d. The volume of international trade has grown rapidly.

Which of the following is not correct about most economic models?

a. They are composed of equations and diagrams. b. They contribute very little to economists' understanding of the real world. c. They omit many features of the real-world economy. d. In constructing models, economists make assumptions.