1.Why is it difficult to test macroeconomic theories?

2.How is the U.S. national economy different from those of other nations?

3.An increase in the sale of new houses is often a sign that an economic expansion is coming. Why would this be the case?

All three response should be at least 75 words in length. All sources used, including the textbook, must be referenced; paraphrased and quoted material must have accompanying citations.