第篇供给与需求.ppt

The first part of the explanation discusses the opposing effects on revenue; its purpose is to clarify the effects of a price decrease on revenue, as we have previously only discussed the effects of a price increase. * The material on this slide is not used anywhere else in the textbook. Therefore, if you are pressed for time and looking for things to cut, you might consider cutting this slide. (Note that this is my personal recommendation and is not necessarily the official position of Greg Mankiw or Cengage/South-Western.) Due to space limitations, this slide uses “E” as an abbreviation for elasticity, or more specifically, the price elasticity of demand, and the slide omits the analysis of revenue along the demand curve. Calculations of percentage changes use the midpoint method. (This is why the increase from Q=0 to Q=20 is 200% rather than infinity.) As you move down a linear demand curve, the slope (the ratio of the absolute change in P to that in Q) remains constant: From the point (0, $30) to the point (20, $20), the “rise” equals -$10, the “run” equals +20, so the slope equals -1/2 or -0.5. From the point (40, $10) to the point (60, $0), the “rise” again equals -$10, the “run” equals +20, and the slope again equals -0.5. However, the percentage changes in these variables do not remain constant, as shown by the different colored elasticity calculations that appear on the slide. The lesson here is that elasticity falls as you move downward rightward along a linear demand curve. * 73 5 * 29 19 * 32 21 * * 32 21 * 37 * 8 7 * 8 7 * 8 7 * 8 7 * 8 7 * 46 * 46 * “Supply” refers to the position of the supply curve, while “quantity supplied” refers to the specific amount that producers are willing and able to sell. Similarly, “demand” refers to the position of the demand curve, while “quantity demanded” refers to the specific amount that consumers are willing and able to buy. If you’d like to be a rebel, delete this slide and all refer