Efficient provision of private goods Derivation of aggregate demand Each person,s demand curve represents the willingness-to-pay for an additional unit of a good Private good: holding P constant, add together individual quantities to get Q Horizonta summation7 Efficient provision of private goods • Derivation of aggregate demand • Each person’s demand curve represents the willingness-to-pay for an additional unit of a good. • Private good: holding P constant, add together individual quantities to get Q. • Horizontal summation