2.2.5—PED on straight-line demand

Even though the slope of a straight-line demand curve is constant, PED changes along it because elasticity uses percentage changes relative to the current price and quantity.

Near the high-price/low-quantity end, a small quantity change is large relative to quantity, so demand is more elastic. Near the low-price/high-quantity end, it is more inelastic; the midpoint is unitary in the standard linear case.

Moving the same small amount along a linear demand curve can produce a larger percentage quantity response near the quantity intercept than near the price intercept.

Constant slope does not mean constant PED; slope and elasticity are different measures.