A Constant Unitary Elasticity Supply Curve

Unlike the unit elastic demand curve, the supply curve with unitary elasticity is a straight line through the origin. Each pair of points is 30 units of quantity apart, but in percentage terms, by the midpoint method, the steps shrink from 28.6% to 22.2% to 18.2% as you move right, because the quantities in each average get larger.

The price steps of $1.50 are likewise the same in absolute value but shrink in percentage terms, from 28.6% to 22.2% to 18.2%, for the same reason. Along the whole line the percentage increase in quantity exactly matches the percentage increase in price, so this supply curve has constant unitary elasticity at every point.