A Monopoly is a market structure characterised by one firm and many buyers, a lack of substitute products and barriers to entry (Pass et al. 2000). An oligopoly is a market structure characterised by few firms and many buyers, homogenous or differentiated products and also difficult market entry (Pass et al. 2000) an example of an oligopoly would be the fast food industry where there is a few firms such as McDonalds, Burger King and KFC that all compete for a greater market share.
In a Monopoly there is one firm that controls the market, and there is no similar products being sold by other companies. Advertising is therefore used to encourage people to buy more of their product. In a monopoly there is a downward sloping demand curve, the reason for this is that a firm must lower the price to sell and extra unit of their product. For a monopoly to maximise profits it must have an equilibrium point where marginal cost equals marginal revenue, there is no reason for a firm to move from this equilibrium point because they are fulfilling their market plan. Using Figure 1 (Stewart, 2005) it can be explained why a monopoly firm would advertise. Marginal cost is fixed and is the line MC and demand is line D, marginal revenue is line MR. As the firm wishes to profit maximise it sets output at level Qm where marginal revenue crosses marginal cost, this means price is set at Pm where the quantity
References: Gillespie, A (2001) AS & A Level Economics through diagrams, Oxford: Oxford University Press Pass, C, Lowes, B and Davies, L (2000) Collins Economics Dictionary, 3rd ed, Glasgow: HaperCollins Powell, R (2003) Module 5: Business Economics and the Distribution of Income, Oxfordshire: Phillip Alan Updates Stewart, G (2005) Advertising, Economist, April 2005, pp14-16