Constant PES on a Linear Supply Curve from the Origin

Steps:

• Define PES as (% change in quantity supplied) / (% change in price).
• Identify the supply curve as linear and passing through the origin, so Q = kP.
• Calculate PES = (dQ/dP) * (P/Q) = k * (P / kP) = 1, constant at all points.
• Confirm no variation in elasticity since P/Q ratio remains fixed along the curve.

Why D is correct:

• For a linear supply curve through the origin, PES equals 1 everywhere per the formula PES = (slope) * (P/Q), as P/Q is constant.

Why the others are wrong:

• A: PES equals unity (1), not greater than 1.
• B: Describes varying PES on upward-intercept curves, but here it's constant.
• C: PES is a point measure and doesn't inherently rise with supply or price on this curve.

Final answer: D