A monopoly is, technically, 100% of the market share; however, getting to that stage is impossible so the legal term of a monopoly is now 25% of the market share. At 25% the competition commission takes a look at the business and at 40% they start to see if it’s in the best interests of the public to split the firm. But monopolies have their advantages.

When a business has a monopoly, the firm benefits from economies of scale: Higher technological positioning (they’re able to buy the newest equipment), bulk buying (which usually brings down the cost to customers) as well as a multitude of other things.

The argument against monopolies is that they can exploit the market and remove fair play by using extreme barriers to entry, look at Microsoft as an example.

In my opinion the legal term of a monopoly needs to be 40% because at 25% there’s still a 75% market against them who are very competitive (look at the supermarkets market share).