Chapter 3: Introduction

Demand and Supply

In this chapter, you will learn to:

  • characterize and give examples of markets
  • describe (consumer) demand and explain how it can change
  • describe (producer) supply and explain how it can change
  • relate how supply and demand interact to determine market equilibrium
  • explain how changes in supply and demand affect equilibrium prices and quantities
  • identify what government-set prices are and how they can cause product surpluses and shortages
  • calculate market demand from individual demand curves


An auction bidder pays thousands of dollars for a dress Whitney Houston wore. A collector spends a small fortune for a few drawings by John Lennon. People usually react to purchases like these in two ways: their jaw drops because they think these are high prices to pay for such goods or they think these are rare, desirable items and the amount paid seems right.

When economists talk about prices, they are less interested in making judgments than in gaining a practical understanding of what determines prices and why prices change. Consider a price most of us contend with weekly: that of a gallon of gas. Why was the average price of gasoline in the United States $3.71 per gallon in June 2014? Why did the price for gasoline fall sharply to $1.96 per gallon by January 2016? To explain these price movements, economists focus on the determinants of what gasoline buyers are willing to pay and what gasoline sellers are willing to accept.

As it turns out, the price of gasoline in June of any given year is nearly always higher than the price in January of that same year. Over recent decades, gasoline prices in midsummer have averaged about 10 cents per gallon more than their midwinter low. The likely reason is that people drive more in the summer, and are also willing to pay more for gas, but that does not explain how steeply gas prices fell. Other factors were at work during those 18 months, such as increases in supply and decreases in the demand for crude oil.

This chapter introduces the economic model of demand and supply—one of the most powerful models in all of economics. The discussion here begins by examining how demand and supply determine the price and the quantity sold in markets for goods and services, and how changes in demand and supply lead to changes in prices and quantities.


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Agribusiness Management 101 Copyright © by William Rossman is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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