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Product differentiation

Product differentiation is crucial to monopolistic competition. In fact, product differentiation is really what stands between perfect competition and the real world. People differentiate among many similar products.

Price discrimination

Price discrimination occurs when a seller charges two or more prices for the same good or service.

Examples:

  1. Doctors often charge rich patients 10 times as much for the same service as poor patients.

  2. Airlines sometimes allow riders under 16 years of age to fly at half-fare ("youthfare").

The firm that practices price discrimination needs to be able to distinguish between two or more separate groups of buyers.

In addition to distinguishing among separate groups of buyers, the price discriminator must be able to prevent buyers from reselling the product (i.e., stop those who buy at a low price from selling to those who would otherwise buy at a higher price).

4. Oligopoly

Unlike a monopolistically competitive market, oligopoly is a market structure in which a few sellers dominate in sales of a product and where entry of new sellers is difficult or impossible. The product can be either differentiated or standardized.

An oligopoly is an industry with just a few sellers. How few? So few that at least one firm is large enough to influence price.

Is the product identical or differentiated? It doesn't matter. In the case of the steel, copper, and aluminum industries, the product happens to be identical; but in most other cases, the product is differentiated.

Concentration ratios

One way of measuring how concentrated an industry is, is to look at the percentage share of sales of the leading firms. This is called the industry's concentration ratio.

Economists use concentration ratios as a quantitative measure of oligopoly.

The total percentage share of industry sales of the four leading firms is the industry concentration ratio. Industries with high ratios are very oligopolistic.

Two key shortcomings of concentration ratios should be noted.

1. Don't include imports.

2. The concentration ratios tell us nothing about the competitive structure of the rest of the industry.

A second way is to calculate the Herfindahl – Hirschman index, which, it turns out, is a lot easier to do than to say.

The Herfindahl Hirschman Index (HHI) is the sum of the squares of the market shares of each firm in the industry.

Example:

We'll start with a monopoly. One firm has all the sales, or 100 percent of the market share. So, its HHI would be 1002, or 100 x 100 = 10,000.

Find the HHI of an industry with just two firms, both of which have 50 percent market shares. Work it out right here:

502 + 502 = 2,500 + 2,500 = 5,000

Find the HHI of an industry that has four firms, each with a 25 percent market share:

252 + 252 + 252 + 252 = 625 + 625 + 625 + 625 = 2,500

The less concentrated an industry, the lower its HHI. And here's one last question. Imagine an industry with 100 firms, each with an equal market share. Without going through all the work, see if you can figure out the HHI.

It would come to 100: 12 + 12 + 12 . . . + 12 = 100.

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