12.1. The wealth effect, interest-rate effect, and exchange-rate effect all help explain why the aggregate demand curve is downward sloping. Phyllis, a fellow student in your Macro class, suggests that the substitution effect that you learned about in Unit 1 also explains why aggregate demand curve is downward sloping. She reasons that since it explains why a market demand curve is downward sloping, it must also be valid for aggregate demand. Explain why Phyllis is wrong.

Which of the statements best describes why the aggregate demand curve is downward sloping? an increase in the aggregate price level causes consumer and investment spending to fall, because consumer purchasing power decreases and money demand increases. as the aggregate price level increases, consumer expectations about the future change. as the aggregate price level decreases, the stock of existing physical capital increases. as a good's price increases, holding all else constant, the good's quantity demanded decreases.