FIGURE D.5 The Changing Slope of an Indifference CurveThis indifference curve is downward-sloping and convex, implying that restaurant meals and rooms are ordinary goods for Ingrid. As Ingrid moves down her indifference curve from V to Z, she gives up restaurant meals in exchange for a larger number of rooms. However, the terms of that trade-off change. As she moves from V to W, she is willing to give up 10 restaurant meals in return for 1 more room. As her consumption of rooms rises and her consumption of restaurant meals falls, she is willing to give up fewer restaurant meals in return for each additional room. The flattening of the slope as she moves from left to right arises from diminishing marginal utility.