How can I prove that the equilibrum point $D(p)=S(p)$ is pareto efficient?
The definition of pareto efficient: there is no way to make any person better off without hurting anybody else
$D(p)$ is the market demand curve and $S(p)$ is the market supply curve
I´m working with Hal Varian intermediate microeconomics and he proves that any amount less than the equilibrium amount cannot be Pareto efficient :
At any amount of output less than the competitive amount $q^*$ there is someone who is willing to supply an extra unit of the good at a price that is less than the price that someone is willing to pay for an extra unit of the good. If the good were produced and exchanged between these two people at any price between the demand price and the supply price, they would both be made better off. Thus any amount less than the equilibrum amount cannot be Pareto efficient, since there will be at least two people who could be better off
But I´m having trouble proving that the equilibrium point is pareto efficient
I would really appreciate if you can help me with this problem. Any comments, or suggestions would be highly appreciated