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2005-03-15
对经济波动的看法

1、流行
流行是一种从众行为。从众是一种群体性行为。个体作决策时,虽然也想使自身利益最大化,但受制于信息的不完全和未来的不确定,个体可能处于一种犹豫不决的状态,即两种选择相比差不多的状态。此时个体的选择可能要参考他人的选择。所以效用函数中,还应包含别人的选择。别人对同种物品或行为的选择越多,对同种物品的选择所带来的期望效用就越大。从众行为恐怕是群体长期进化而来的一种理性选择。物种在长期的生存斗争中,可能要经常性的同外界斗争。在同外界的斗争中要想取胜,可能需要群体的共同努力和一致的行为。所以拥有从众行为或集体行为的物种生存下来,而喜欢独立奋斗的物种则易于灭亡。人类的从众行为根植于人类的基因和大脑的潜意识之中。但是从众行为并不一定正确,有时也出错。
从众行为,安全感,归属感,个体对群体的归属,群体对个体的接纳。
扩散机制。一种现象行为的出现,小范围的扩散,大范围的扩散,同时改变影响决定其生存和发展的重要因素,于是自我维持。于是占了统治地位,并且自我维持巩固。扩散,生物学中物种数量增长的逻辑斯递模型。
从众行为:预期效用最大化,前景的不明朗,个人的效用函数中包含他人的选择。个人的这种从众行为是生物进化自然选择的结果。
U=u(x1,x2) x1自己的选择,x2他人的选择
Du/dx1>0 du/dx2>0

2、预期
人们的投资和消费行为无时无刻不受着预期的影响。预期是人们对未来前景的主观看法。人们试图知道未来,但人们无法精确的预测未来。人类的预期除了靠理性思维外,也受着感性思维的支配,受到情绪的支配。人们在做出投资决策时,除了要计算投资成本外还要预测市场前景。投资成本相对容易计算。市场前景的不确定因素太多,不仅要看需求方的反应,还要看技术的发展,竞争者的反应。于是人们预测市场前景近乎主观估计。而且如果想预测整个经济形势更靠经验法则。大量的企业家作决策靠的是拍脑袋,靠的是胆识。
个体对未来的预期很难说十分自信。当个体犹豫不决时,就容易受到别人的选择的影响。有时别人的选择未必适合自己,有时对单个人最优的行为会造成群体的非优。比如着火时大家抢着出门,会互相践踏或造成拥堵。做投资决策时往往会一窝蜂的投资向某个产业。这在我国屡见不鲜。

3、信用的作用,金融的作用
银行通常是贷款给投资者而非消费者,当然这并不是说这个社会就没有消费贷款,而是说投资的贷款比例更大。与企业的流动性约束相比,个人的流动性约束更加严重。企业借了钱可以钱生前,而且通常企业通常有抵押品和担保人,而个人的收入增长幅度有限,而且没有或只有少量抵押品,人们一般习惯于量入为出,而非借钱消费。因为未来是不确定的。除了住房、汽车等耐久性大额消费品之外,一般人很少贷款消费。信用在投资和消费中的不平衡性导致了投资和消费不同的变化速度。

4、产业链
经济中的产业链类似于生态系统中的生态链。经济中的企业不是一样的同质的,而是分属于不同的群体,即产业。物质和能量在产业链中传递,产品经过层层加工,最终为个人所消费。货币是交换的媒介。产业链中传递的不仅有物质和能量还有相反方向运动的货币。空间是经济活动中一种重要的因素,空间的使用权货币化了,体现了空间的价值。货币在产业链中的传递是需要时间的,而不是瞬时的,这种时间是不可以忽略不计的,而是要对经济活动产生了重大的影响的。货币在产业链中传递的时间包括几种:认识时间,决策时间,投资时间,生产时间,销售时间。货币在产业链中的运动速度受技术,个体认识世界的程度和经济制度的制约。

5、经济波动
经济波动应该是内生的,是由一种力量增长的同市另一种相反的力量的积累,从而此消彼长的周期性行为。而不应看成是由于外生力量冲击引起的。拿物理学钟摆的例子做类比。当钟摆处于最高点时,动能为零,势能最大;受引力作用,钟摆开始加速,动能逐渐转变为势能;在最低点动能最大,势能最小;同样受引力作用,钟摆越过最低点,动能逐渐减少,势能逐渐变大。于是又达到另一端的最高点,动能为零,势能最大。于是又开始新的周期运动。经济中的利润类似于物理学中的力。企业的行为无时不是受着利润的驱动。
经济中存在着两种力量,走向均衡的力量和背离均衡的力量。这两种力量的此消彼长造成经济的自发的有周期的节律性运动。均衡的力量限制了经济波动的幅度,非均衡的力量造成经济的波动。货币在产业链中的传递速度、社会的理性及非理性程度制约着经济波动的频率。社会对经济波动的记忆以及由此带来的社会对经济的有意识调控逐渐改变着经济波动的形式。可以大致计算经济周期的波幅和周期。可能会用到差分方程和偏微分方程组。
均衡是相对的,不均衡是绝对的。假设市场是垄断竞争的,可以自由的进入和退出。假设技术进步看成是静止的。假设政府不干预市场。
扩张初期。假设一开始消费品需求略大于供给,企业的反应是提价增产。增产就有两种作用:雇佣更多的人,发更多的工资,增加新的投资。这些新工资和新投资都会顺着产业链传递,造成总产出和消费品需求的些许增长。
扩张蔓延期和繁荣期。由于更多的工资造成消费品需求的持续增长,在先发企业的利润增加的示范效应下,由于群体从众心理、过度自信、无序竞争,更多的资本包括投机性资本涌入。由于信息的不完全,人们并不知道将会有多少人涌入。而且大量新投资会对下游产业造成强劲的需求,这种繁荣的景象会沿着整个产业链传递。各产业依次的逐步的繁荣,会给人产生一种过度良好的预期,并进一步加速了新的资本的涌入。银行和其他金融组织起了通过信用的放大进一步加强了这种情况。此时个人的收入虽然由于经济的繁荣而增加了,但是增加的幅度远没有投资的增加速度快。收入分配和信用发展的不平衡进一步加强了这种趋势。这种结构不平衡就为将来的衰退埋下了种子。马克思说的大概就是这个意思。
衰退。由于消费的增长是经济增长的最终的目的。但是由于从众行为和信用膨胀使对消费品的供给突然大于需求。在这种供大于求的情况下,市场开始重新整合。实力小的企业破产或者被收购或者被迫转产。无论何种方式这种企业都会付出很大的代价。即使是先入者或实力雄厚者也会在市场压力下降价减产。无论何种情况下,都不会给新的投资,存货的减少是负投资,折旧也是负投资。这时对上游产业的需求就减少了,银行也很少贷款了。于是衰退沿着整个产业链传递。社会开始笼罩一种悲观的情绪。经济的主旋律成了破产,失业,降工资。银行会形成大量坏账,金融体系受到打击,进一步打击企业。投资变得很少,有些公司仅弥补折旧,有些公司则负投资。总体上经济向下运行。
复苏。低谷中投资的减少、供给的减少要远远大于消费品需求的减少。投资品需求的变动率大于消费品需求的变动率是经济运动的一个基本规律。在衰退中生存下来的企业逐渐的整合市场,积累资本,准备新投资。随着繁荣时积累的大量存货的逐步减少,企业有采购新的原料。随着资本的折旧企业要购买新的资本品。这时对投资品的需求就复苏了。就业增加,个人收入增加,消费品需求也就复苏了。于是经济开始了下一轮循环。
按照上述推理,经济波动中应该存在着:
1、 产业内部的变迁。
2、 消费品需求的变动小于投资品需求的变动。
3、 复苏和衰退沿产业链的传递。
4、 社会整体对经济的信心的交替变化。
5、 盲目扩张和大量破产的交替。
这些现象可以用来验证和推翻上述想法。

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全部回复
2005-3-20 15:06:00

“人类的从众行为根植于人类的基因和大脑的潜意识之中”

无论“根源”怎样“不可捉摸”,想以此做分析,就必须对“从众行为”给出一个公理化的具有确定含义的表达式。这种表达式的内容应该是可观测的,或者说在观测的意义上是可以理解的。

“U=u(x1,x2) x1自己的选择,x2他人的选择,Du/dx1>0 du/dx2>0”

“效用”、“(自己或他人的)选择”各是如何定义的?

“可能会用到差分方程和偏微分方程组”

说几千字都不如直接给出这些方程,我们急切想看到的就是这些方程,它们几乎是本文的全部意义所在。

如果牛顿不给出万有引力定律的具体表达式,只说太阳与地球相互吸引,这种定律有什么物理意义吗?为什么地球不坠到太阳,不远离太阳,偏偏要“围着”太阳“转”?

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2005-3-21 22:21:00

太阳对月球的引力远大于地球对它的引力

为什么月球不是围着太阳转???

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2005-3-31 20:28:00

太阳对地球引力大于地球对太阳引力?天!

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2005-3-31 23:36:00
我觉得RBC模型的解释力还是非常好的.
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2005-4-1 10:41:00

The Influence of the Natural Sciences on the Social Sciences

In the course of its slow development in the eighteenth and early nineteenth centuries the study of economic and social phenomena was guided in the choice of its methods in the main by the nature of the problems it had to face. 1.1 It gradually developed a technique appropriate to these problems without much reflection on the character of the methods or on their relation to that of other disciplines of knowledge. Students of political economy could describe it alternatively as a branch of science or of moral or social philosophy without the least qualms whether their subject was scientific or philosophical. The term science had not yet assumed the special narrow meaning it has today,1.2 nor was there any distinction made which singled out the physical or natural sciences and attributed to them a special dignity. Those who devoted themselves to those fields indeed readily chose the designation of philosophy when they were concerned with the more general aspects of their problems,1.3 and occasionally we even find ``natural philosophy'' contrasted with ``moral science.''

During the first half of the nineteenth century a new attitude made its appearance. The term science came more and more to be confined to the physical and biological disciplines which at the same time began to claim for themselves a special rigorousness and certainty which distinguished them from all others. Their success was such that they soon came to exercise an extraordinary fascination on those working in other fields, who rapidly began to imitate their teaching and vocabulary. Thus the tyranny commenced which the methods and technique of the Sciences1.4 in the narrow sense of the term have ever since exercised over the other subjects. These became increasingly concerned to vindicate their equal status by showing that their methods were the same as those of their brilliantly successful sisters rather than by adapting their methods more and more to their own particular problems. And, although in the hundred and twenty years or so, during which this ambition to imitate Science in its methods rather than its spirit has now dominated social studies, it has contributed scarcely anything to our understanding of social phenomena, not only does it continue to confuse and discredit the work of the social disciplines, but demands for further attempts in this direction are still presented to us as the latest revolutionary innovations which, if adopted, will secure rapid undreamed of progress.

Let it be said at once, however, that those who were loudest in these demands were rarely themselves men who had noticeably enriched our knowledge of the Sciences. From Francis Bacon, the lord chancellor, who will forever remain the prototype of the ``demagogue of science,'' as he has justly been called, to Auguste Comte and the ``physicalists'' of our own day, the claims for the exclusive virtues of the specific methods employed by the natural sciences were mostly advanced by men whose right to speak on behalf of the scientists was not above suspicion, and who indeed in many cases had shown in the Sciences themselves as much bigoted prejudice as in their attitude to other subjects. Just as Francis Bacon opposed Copernican astronomy,1.5 and as Comte taught that any too minute investigation of the phenomena by such instruments as the microscope was harmful and should be suppressed by the spiritual power of the positive society, because it tended to upset the laws of positive science, so this dogmatic attitude has so often misled men of this type in their own field that there should have been little reason to pay too much deference to their views about problems still more distant from the fields from which they derived their inspiration.

There is yet another qualification which the reader ought to keep in mind throughout the following discussion. The methods which scientists or men fascinated by the natural sciences have so often tried to force upon the social sciences were not always necessarily those which the scientists in fact followed in their own field, but rather those which they believed that they employed. This is not necessarily the same thing. The scientist reflecting and theorizing about his procedure is not always a reliable guide. The views about the character of the method of Science have undergone various fashions during the last few generations, while we must assume that the methods actually followed have remained essentially the same. But since it was what scientists believed that they did, and even the views which they had held some time before, which have influenced the social sciences, the following comments on the methods of the natural sciences also do not necessarily claim to be a true account of what the scientists in fact do, but an account of the views on the nature of scientific method which were dominant in recent times.

The history of this influence, the channels through which it operated, and the direction in which it affected social developments, will occupy us throughout the series of historical studies to which the present essay is designed to serve as an introduction. Before we trace the historical course of this influence and its effects, we shall here attempt to describe its general characteristics and the nature of the problems to which the unwarranted and unfortunate extensions of the habits of thought of the physical and biological sciences have given rise. There are certain typical elements of this attitude which we shall meet again and again and whose prima facie plausibility makes it necessary to examine them with some care. While in the particular historical instances it is not always possible to show how these characteristic views are connected with or derived from the habits of thought of the scientists, this is easier in a systematic survey.

It need scarcely be emphasized that nothing we shall have to say is aimed against the methods of Science in their proper sphere or is intended to throw the slightest doubt on their value. But to preclude any misunderstanding on this point we shall, wherever we are concerned, not with the general spirit of disinterested inquiry but with slavish imitation of the method and language of Science, speak of scientism or the scientistic prejudice. Although these terms are not completely unknown in English,1.6they are actually borrowed from the French, where in recent years they have come to be generally used in very much the same sense in which they will be used here.1.7It should be noted that, in the sense in which we shall use these terms, they describe, of course, an attitude which is decidedly unscientific in the true sense of the word, since it involves a mechanical and uncritical application of habits of thought to fields different from those in which they have been formed. The scientistic as distinguished from the scientific view is not an unprejudiced but a very prejudiced approach which, before it has considered its subject, claims to know what is the most appropriate way of investigating it.1.8

It would be convenient if a similar term were available to describe the characteristic mental attitude of the engineer which, although in many respects closely related to scientism, is yet distinct from it but which we intend to consider here in connection with the latter. No single word of equal expressiveness suggests itself, however, and we shall have to be content to describe this second element so characteristic of nineteenth- and twentieth-century thought as the ``engineering type of mind.''

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The Counter-Revolution of Science

Studies on The Abuse of Reason

F. A. Hayek

[此贴子已经被作者于2005-4-1 10:43:04编辑过]

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