5.11 : 無差別曲線の種類

The indifference curves are typically convex to the origin.

This shape changes if the products are perfect substitutes or complements.

Neil works out daily. He uses coconut water and sports drinks to replenish electrolytes throughout the day. He uses these as substitutes.

His preference can be shown on indifference curve IC1. Moving from point A to point B, Neil trades equal amounts of coconut water for sports drinks. This results in a straight-line indifference curve.

Neil views mobile phones and phone cases as perfectly complementary products. Point A shows one mobile phone and one phone case. Neil gets satisfaction from such complete pairs.

Moving vertically upward from Point A, no matter how many extra phone cases he buys each year, his utility remains constant. Also, moving horizontally rightwards from this point, the extra mobile phones that he gets can not be used without more phone cases because of the risk of damage. So, the indifference curve consists of straight lines that meet at 90-degree angles.

It follows that indifference curves are straight lines for perfectly substitute goods and right-angled for perfectly complementary goods.