交叠世代模型
参考答案：
交叠世代模型，由萨缪尔森首创，针对货币经济理论缺乏微观基础这一缺陷，从货币的价值储藏职能出发，研究人们为什么要持有货币、货币在何种条件下具有正价值，并在此基础上建立的货币分析理论模型。交叠世代模型认为，在任何一个时刻都有不同代的人活着，每一代人在其生命的不同时期都可以和不同代的人进行交易。他们的消费、储蓄、投资等所有经济选择，由于身处不同代际（即处于不同的年龄段），必然表现出不同的行为方式，即不同代际的人之间的交往规律不尽相同，因此，整个经济就构成了一个复杂的有机体。交叠世代模型的基本形式是一个跨时的一般均衡模型。
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| What will city life be like in the future? Some people think that life in the cities is going to be 1 . They 2 that cities will become more and more crowded. 3 the number of people increases, there will be less space for each person. This 4 will cause other problems-more crimes, dirtier streets, and worse problems with traffic 50 we have now. How will people find enough drinking water, energy (such as gas and electricity), and housing? 6 life will be hard, people who live in cities will worry more, and they may become sick. 7 these reasons, some say that nobody will want to live in urban areas. How can we 8 such problems as overcrowding, crime, and traffic? In some cities, thousands of people are already 9 in the streets because there is so little suitable housing-and because 10 are so high. The crime rate isn't going down. 11 , it is, 12 so fast that many people are afraid to go out at night. Traffic jams are so bad that cars don't move at all for several blocks. These 13 problems have been getting worse, not better, so many people see no 14 for the future of the city. However, not all people believe in the horrible 15 for cities of the future. Instead, they feel that they can solve present urban problems and 16 future ones. The disadvantages of any modem city are not unique (独特的) to that city. 17 , all the cities in the world have to solve the problems of traffic jams, crime, housing, energy, drinking water and overcrowding. Yet many cities have found answers to one or more of these difficulties. Some European cities, such as Stockholm, Sweden, or London, England, have planned communities that 18 people with apartments, jobs, shopping centers, green space, entertainment and transportation. Many U.S. cities are building their downtown areas. Urban 19 can learn from one another. They can 20 solutions that have been successful in other parts of the world. | ||||
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