Elasticity (Economics)

Recall cards on elasticity, the measure of how responsive quantity is to price. Price elasticity of demand and of supply as ratios of percentage changes, why the demand elasticity is negative but reported as an absolute value, and the elastic (greater than 1), unitary (equal to 1), and inelastic (less than 1) ranges. The midpoint method and why it gives the same value whether price rises or falls, and how elasticity differs from slope. The polar cases: perfectly elastic (a horizontal line), perfectly inelastic (a vertical line), and constant unitary elasticity. How elasticity determines who bears a tax and how a price change moves total revenue when demand is elastic, inelastic, or unitary, plus the short-run versus long-run difference. Finally, elasticity beyond price: income elasticity and normal versus inferior goods, cross-price elasticity and substitutes versus complements, and the wage and savings elasticities.