Consider a graph where the quantity of good X is represented on the x-axis and the quantity of good Y on the y-axis. If the indifference curves are concave toward the origin, how does the marginal rate of substitution of good Y for good X (the slope of the indifference curve) change as we move from a situation with a large amount of good X to one with a large amount of good Y?
Explanation
When indifference curves are concave (bowed inward), the marginal rate of substitution of good Y for good X rises as we shift from having mostly good X to mostly good Y. This means the consumer is willing to give up more of good X to obtain an additional unit of good Y as their consumption changes.