PRICE ELASTICITY OF SUPPLY AND THE SLOPE OF THE SLOPE CURVE

For a straight line supply curve, the gradient is constant along the whole length of the curve, but elasticity is not necessarily constant.  However, at any given point the steeper the supply curve, the more inelastic will be the supply.  For this reason, steeply sloped supply curves are usually associated with inelastic supply and non-steeply sloped supply curves are usually associated with elastic supply.

In the first diagram, when price increases from P₁ to P₂, quantity supplied increases in less proportion from q₁ to q₂.  Conversely, when price falls from P₂ to P₁, quantity supplied falls in less proportion from q₂ to q₁.

In the second diagram, when price rises from P₁₁ to P₂₁, quantity supplied rises in greater proportion from q₁₁ to q₂₁, and when price falls from P₂₁ to P₁₁, quantity supplied falls in greater proportion from q₂₁ to q₁₁.