Constant Elasticity Supply Curve

Steps:

• Recall price elasticity of supply (Es) measures responsiveness of quantity supplied to price changes: Es = (%ΔQ)/(%ΔP).
• Constant Es means the ratio remains fixed along the curve, implying a proportional relationship between P and Q.
• Identify curves: vertical (Es=0), horizontal (Es=∞), linear through origin (constant Es>0), and nonlinear (varying Es).
• Select the curve where slope adjusts to keep Es constant, typically a straight line from origin.

Why C is correct:

• Curve C is a ray from the origin, where Q = kP and Es = 1 (unit elastic), constant by definition.

Why the others are wrong:

• A: Vertical line; Es=0 (perfectly inelastic), not constant unless zero everywhere.
• B: Horizontal line; Es=∞ (perfectly elastic), not constant.
• D: Nonlinear/upward-curving; Es varies (increases with P), not constant.

Final answer: C