Keynesian cross
凯恩斯交叉
This model is the simplest interpretation of Keynes's theory of how national income is determined.
这个模型是凯恩斯关于国民收入如何被决定的理论的最简单解释
In The General Theory, Keynes proposed that an economy's total income is, in the short run, determined largely by the spending plans of households, businesses, and government. The more people want to spend, the more goods and services firms can sell. The more firms can sell, the more output they will choose to produce and the more workers they will choose to hire. Keynes believed that the problem during recessions and depressions is inadequate spending. The Keynesian cross is an attempt to model this insight.
在“通论”中,凯恩斯提出经济的总收入在短期内主要由家庭,企业和政府的支出计划决定。 越多的人想要消费,公司可以销售越多的商品和服务。 公司可以销售的商品和服务越多,他们选择生产的产出越多,他们将选择聘用的工人越多。 凯恩斯认为,经济衰退和萧条期间的问题是支出不足。凯恩斯交叉是对这种见解建模的尝试。
Planned expenditure is the amount households, firms, and the government would like to spend on goods and services.(记住would like to spend/buy)
计划支出是家庭、企业和政府想花在产品和服务上的数额。
Actual expenditure is the amount households, firms, and the government spend on goods and services.
实际支出是家庭、企业和政府花在产品和服务上的数额。
The next piece of the Keynesian cross is the assumption that the economy is in equilibrium when actual expenditure equals planned expenditure. This assumption is based on the idea that when people's plans have been realized, they have no reason to change what they are doing.
凯恩斯交叉是假设当 实际支出=计划支出 时,经济处于均衡状态。
这个假设是基于:当人们的计划实现时,他们没有理由改变他们当前的行为。
例如:我今天想买1件衣服,结果我去买了1件衣服,我实现了我的计划,不再改变当前的行为。
1、关于理解企业是减少生产还是增加生产
计划支出是家庭、企业和政府 would like to spend/buy 的
计划支出PE 小于 实际支出Y 就是家庭、企业和政府 would like to spend/buy 的数量少了,那么企业销售的低于其生产的,产品卖不完,企业减少生产。
所以,计划支出PE实际支出Y
企业增加生产
2、增加生产和减少生产怎么让经济达到均衡
Why would actual expenditure ever differ from planned expenditure? The answer is that firms might engage in unplanned inventory investment because their sales do not meet their expectations. When firms sell less of their product than they planned, their stock of inventories automatically rises; conversely, when firms sell more than planned, their stock of inventories falls. Because these unplanned changes in inventory are counted as investment spending by firms, actual expenditure can be either above or below planned expenditure.
为什么实际支出与计划支出有所不同?答案是公司可能会从事无计划的库存投资,因为他们的销售额不符合他们的预期。当公司比他们计划的销售更少的产品时,他们的库存量会自动增加;相反,当公司比计划销售更多时,他们的库存量就会下降。因为这些计划外的库存变化被视为企业的投资支出,所以实际支出可以高于或低于计划支出。
图片来自人民大学版曼昆宏观经济学第七版
关于为什么计划支出曲线不是一条斜率为0的线?
请注意这个图的横轴和纵轴索表示的。横轴表示收入水平Y,纵轴表示计划支出PE,计划支出PE是收入水平Y的函数。
如果计划支出曲线是一条斜率为0的线,那么就变成了随着收入Y变化,计划支出(would like to spend/buy)不变,这是不对的,因为较高的收入导致较高的消费从而导致较高的计划支出C=C(Y-T),PE=C(Y-T)+I+G,假设了T I G都是外生变量 随着收入增加would like to spend/buy的也增加。
为什么实际支出曲线是一条斜率为1,倾角45度的线?
依然请注意这个图的横轴和纵轴所表示的。
因为只有当这条线的倾角为45度时,才能满足“这条线上的任何一点,到横轴和纵轴的垂直距离都相等”这个条件,也就是满足 计划支出=实际支出,符合假设:凯恩斯交叉是假设当 实际支出=计划支出 时,经济处于均衡状态。
参考文献/知识来源:
曼昆宏观经济学第七版 人民大学出版社
Principle of Microeconomics , 7th , Mankiw Worth Publishers
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