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se the products are not exactly the same, each seller has some ability to set the price for its own product. An example is the software industry. Many word processing programs pete with one another for users, but every program is different from every other and has its own price. Despite the diversity of market types we find in the world, we begin by studying perfect petition. Perfectly petitive markets are the easiest to analyze. Moreover, because some degree of petition is present in most markets, many of the lessons that we learn by studying supply and demand under perfect petition apply in more plicated markets as well. DEMAND We begin our study of markets by examining the behavior of buyers. Here we consider what determines the quantity demanded of any good, which is the amount of the good that buyers are willing and able to purchase. To focus our thinking, let39。 當(dāng)中東爆發(fā)戰(zhàn)爭時(shí),美國的汽油價(jià)格上升,而二手凱迪拉克轎車價(jià)格下降 。本章要說明市場經(jīng)濟(jì)中供給與需求如何決定價(jià)格,以及價(jià)格又如何配置經(jīng)濟(jì)的稀缺資源 。 更經(jīng)常的情況是,市場并沒有什么組織 。 確切地說,冰激凌的價(jià)格和銷售量是由所有買者和賣者在市場上的相互交易所決定的 。 可以根據(jù)兩個基本特征來定義完全競爭市場:( 1)所提供銷售的物品是完全相同的,以及( 2)買者和賣者如此之多,以至于沒有一個買者或賣者可以影響市場價(jià)格 。 例如,你們本地的有線電視公司可能就是一種壟斷 。 這種市場被稱為壟斷 。 為了集中思考,我們牢記一種物品 ——冰激凌 。 收入 : 如果某個夏天你失去了工作,你對冰激凌的需求會發(fā)生什么變化呢?很可能的情況是,需求要減少 。 需求規(guī)律表明你將多買冷凍酸奶 。 當(dāng)一種物品價(jià)格下降增加了另一種物品的需求時(shí),這兩種物品被稱為互補(bǔ)品、其他成對的互補(bǔ)品包括汽油與汽車,電腦和軟件,以及雪橇和空中纜車票 。 需求表與需求曲線 我們已經(jīng)知道,有許多變量決定一個人對冰激凌的需求量 。 表 B1是一個需求表,即一個表示一種物品價(jià)格與其需求量之間關(guān)系的表 。 現(xiàn)在讓我們來考慮價(jià)格如何影響需求量 。 如果你喜歡冰激凌,你會買得多一些 。 因?yàn)楸ち韬屠鋬鏊崮潭际抢涠鸬哪逃吞鹗?,它們滿足相似的欲望 。 如果當(dāng)收入減少時(shí),一種物品的需求減少,這種物品就被稱為正常物品 。 你如何決定每個月買多少冰激凌,以及哪些因素影響你的決策呢?這里是一些你可以給出的回答 。 許多文字處理程序都在相互爭奪使用者,但每一種程序都與其他每一種程序不同,并且有自己的價(jià)格 。 一些市場只有幾個賣者,而且這 些賣者并不總是主動地進(jìn)行競爭 。 有一些市場完全適用于完全競爭的假設(shè) 。 競爭市場是有許多買者與賣者,以至于每一個人對市場價(jià)格的影響都微乎其微的市場 。 冰激凌的買者并沒有在任何一個時(shí)間相聚在一起 。 市場是某種物品或勞務(wù)的一群買者與賣者 。 供給與需求是經(jīng)濟(jì)學(xué)家最常用的兩個詞 ——而且有充分的理由 。s tastes because tastes are based on historical and psychological forces that are beyond the realm of economics. Economists do, however, examine what happens when tastes change. Expectations: Your expectations about the future may affect your demand for a good or service today. For example, if you expect to earn a higher ine next month, you may be more willing to spend some of your current savings buying ice cream. As another example,if you expect the price of ice cream to fall tomorrow, you may be less willing to buy an icecream cone at today39。s keep in mind a particular good— ice cream. WHAT DETERMINES THE QUANTITY AN INDIVIDUAL DEMANDS Consider your own demand for ice cream. How do you decide how much ice cream to buy each month, and what factors affect your decision? Here are some of the answers you might give. Price: If the price of ice cream rose to $20 per scoop, you would buy less ice cream. You might buy frozen yogurt instead. If the price o