Economists object to monopolies on the grounds of efficiency

Economists object to monopolies on the grounds of efficiency. Why is this? Carefully explain.

Solution

A monopolist main purpose is to maximize it\'s profit, so for maximising profit, a monopolist reduce quantity supplied and so the price rises due to excess demand, so due to reduction in the quantity supplied, there is market distortion and so dead weight loss arises. Hence a monopolist market is inefficient.

But in the case of perfect competition, there is no deaf weight loss because here the profit maximising condition is

Price=MC,

So the perfect competitive market is efficient because there is no dead weight loss.