1、附录 A A.1 THE MARKET FORCES OF SUPPLY AND DEMAND When a cold snap hits Florida， the price of orange juice rises in supermarkets throughout the country When the weather turns warm in New England every summer， the price of hotel rooms in the Caribbean plummets When a war breaks out in the Middle East，
2、the price of gasoline in the United States rises， and the price of a used Cadillac falls What do these events have in common? They all show the workings of supply and demand Supply and demand are the two words that economists use most oftenand for good reason Supply and demand are the forces that ma
3、ke market economies work They determine the quantity of each good produced and the price at which it is sold If you want to know how any event or policy will affect the economy， you must think first about how it will affect supply and demand This chapter introduces the theory of supply and demand It
4、 considers how buyers and sellers behave and how they interact with one another It shows how supply and demand determine prices in a market economy and how prices， in turn， allocate the economys scarce resources A.1.1 MARKETS AND COMPETITION The terms supply and demand refer to the behavior of peopl
5、e as they interact with one another in markets A market is a group of buyers and sellers of a particular good or service The buyers as a group determine the demand for the product， and the sellers as a group determine the supply of the product Before discussing how buyers and sellers behave，lets fir
6、st consider more fully what we mean by a “market” and the various types of markets we observe in the economy A.1.1.1 COMPETITIVE MARKETS Markets take many forms Sometimes markets are highly organized， such as the markets for many agricultural commodities In these markets， buyers and sellers meet at
7、a specific time and place， where an auctioneer helps set prices and arrange sales More often， markets are less organized For example， consider the market for ice cream in a particular town Buyers of ice cream do not meet together at any one time The sellers of ice cream are in different locations an
8、d offer somewhat different products There is no auctioneer calling out the price of ice cream Each seller posts a price for an ice-cream cone，and each buyer decides how much ice cream to buy at each store Even though it is not organized， the group of ice-cream buyers and ice-cream sellers forms a ma
9、rket Each buyer knows that there are several sellers from which to choose， and each seller is aware that his product is similar to that offered by other sellers The price of ice cream and the quantity of ice cream sold are not determined by any single buyer or seller Rather， price and quantity are d
10、etermined by all buyers and sellers as they interact in the marketplace The market for ice cream， like most markets in the economy， is highly competitive A competitive market is a market in which there are many buyers and many sellers so that each has a negligible impact on the market price Each sel
11、ler of ice cream has limited control over the price because other sellers are offering similar products A seller has little reason to charge less than the going price， and if he or she charges more， buyers will make their purchases elsewhere Similarly， no single buyer of ice cream can influence the
12、price of ice cream because each buyer purchases only a small amount In this chapter we examine how buyers and sellers interact in competitive markets We see how the forces of supply and demand determine both the quantity of the good sold and its price A.1.1.2 COMPETITION： PERFECT AND OTHERWISE We assume in this chapter that markets are perfectly competitive Perfectly competitive markets are defined by two primary characteristics： (1) the goods being offered for sale are all the same， and (2) the buyers and sellers are so numerous that no single buyer or seller can
