The development of modern finance
First, the financial problem of the uncertainty
(A) the uncertainty of the field in the application of asset pricing
1. Portfolio Theory and Capital Asset Pricing Model
In the framework of the financial analysis, introduction of the concept of uncertainty is a major role. First Kenes (1936) and Hicks (1939) proposed the concept of risk compensation that the financial products in the presence of uncertainty, should interest rates in different financial products in compensation for additional risks. Subsequently, Von Neumann (1947) applied the concept of expected utility of the proposed settlement in the decision-making under uncertainty in the method chosen, on this basis Markowiz (1952) developed a portfolio theory, he thought when investors choose portfolio concerned only with future cash flow of the mean and variance. He assumed that the expected utility of investors consistent with secondary distribution or multinomial distribution. Markowiz The main conclusions are subject to uncertainty, optimal decision-making is a diversified investment holding. Tobin (1958) that investor liquidity preferences for their own benefits and risks of different options for the balance. This further improved the framework of portfolio choice theory.
In the field of asset pricing model is another well-known theory of capital pricing model (CAPM), Sharp (1994) and Lintner (1995) using the formula succinctly expressed the portfolio value and risk-free interest rate and the level of risk assets, the relationship between . Black (1972) introduced even in the non-risk assets zones remained the case, Sharp and the CAPM formula is still valid, just without the risk of interest rates are including the entire market on all assets of the portfolio rate of return instead of the 预期. Contemporary with the CAPM model of the asset pricing model also Ross (1977) arbitrage pricing model (APT) and Lucas (1978) the typical agent asset pricing model.
Represented by CAPM asset pricing model for asset pricing provides a simple method of calculation, and obtain some support from empirical studies (Fama and Macbeth, 1973), but in reality some of the anomalies is still a lack of effective explanatory power, Brennan (1989) that the CAPM is based on the expectations of all investors in the investment and risk are common in estimates and judgments, and all investors the same utility function based on the assumption that this assumption is inconsistent with the reality This is leading to some practical problems CAPM on the root causes of the lack of explanatory power. It is beyond doubt on these assumptions, to promote the introduction of the concept of asymmetric information and research.
2. Market efficiency hypothesis
Market efficiency hypothesis that in a perfectly competitive market, there is no asymmetric information and market frictions affect the future earnings of the average investment risk is different. 60s in the 20th century a large number of research workers on the market efficiency hypothesis was tested, Fama (1973) through empirical tests on the U.S. stock market, that the efficient market hypothesis holds, but many researchers found that in the market, There are many market efficiency hypothesis or CAPM model can not explain the abnormal phenomenon. For example, Basu (1977) found that the average earnings assets, in addition to the β coefficient of the CAPM, but also with the price earnings ratio of assets (P / E ratio) is related to the same β coefficient, the higher the price earnings ratio stocks (growth stocks) better than the market price of the low price earnings ratio of stocks (value stocks); Benz (1981) found that the market price of the stock with the size of the listed company; Stattman (1980) found that stock prices and the ratio of book value (P / B ratio) is also an important factor affecting stock prices. Fama and French (1993) On the basis of the above three-factor model proposed that the impact of asset prices in the β factors, joined the P / E ratio and P / B ratio factor.
The interpretation of these anomalies, the efficient market hypothesis seems powerless, someone had tried the "January effect" to the end of Shuishou interpreted as the impact of outflow, but in the United Kingdom, Australia, the annual revenue of the country is not in December, there are still "in January effect "can not be explained. Some scholars from a psychological perspective to explain these anomalies, such as, Dreman (1982) the stock price P / E ratio effect interpreted as the investor always overestimate growth stocks with high growth, leading to market high P / E ratio of stock market was overvalued, that it is a reason for low stock returns.
3. Continuous time model
In asset pricing theory is another important assumption: stock market is always in a continuous process, under this assumption, Merton (1969,1971) to develop instantaneous CAPM Capital Asset Pricing Model (ICAPM), the same information symmetry, frictionless market, asset price changes in line with Ito process under these conditions, asset prices and investor preference for independent effectiveness. In subsequent studies Merton (1973) and Black (1973) The application of these continuous-time model has been successful in the option pricing formula, the formula was later confirmed that a large number of empirical studies and has been widely applied in practice.
(B) the uncertainty of financial management in the company of
Financial analysis is another important area of financial management, major research firms in the investment decision-making in the proportion of the debt and equity options, the company's dividend policy and other issues. Results of the first studies in this area by the Modigliani and Miller (1958) made their study shows that full market (no market frictions and asymmetric information exists) the value of the company has nothing to do with the company's debt ratio (MM theorem). A similar study concludes that the value of the company's profit distribution policy has nothing to do. Obviously, these research findings and practical in reality. MM theorem based on the conclusions in the distribution of profits, due to the cash outflow will be sent found Jinhong Li, the Company repurchased shares will be more willing to choose policies, rather than the dividend policy, in reality, many companies prefer to dividends rather than Share buy-back, this phenomenon is Black (1976) referred to as "Company dividend puzzle (Dividend Puzzle)", which Miller (1977) can give the explanation, MM theorem conclusion is that the reason and the reality of different tax and the so-called bankruptcy costs on the financial structure is the result of certain liabilities of the company can achieve the role of tax relief, another company because of the existence of high debt ratio risk of bankruptcy, so the debt ratio to the value of existing shares affected, Miller and Other scholars make on these financial problems are not very satisfactory interpretation of the whole until later after the introduction of asymmetric information, it seems Caidui explain these issues to achieve a breakthrough.
As mentioned above, some of the phenomena of reality is difficult to simply use the uncertainty (risk) to get a satisfactory explanation, it is in the research of these issues raises the question of asymmetric information on financial concerns, plus last 60 years in the 20th century to game theory, represented a breakthrough in the information economy research methods, leading many scholars to the financial problems of asymmetric information in the study achieved a lot, especially the use of asymmetric information can explain a lot of perfectly the financial structure issues. Following is an overview of this still results in two parts, first in the results of financial decision-making, followed by the asset pricing results.
(A) asymmetric information in corporate financial management application
Financial order and financial development, innovation and financial imbalances, lack of financial supervision, financial crisis, the United States is an important reason.
In addition, the financial ecology, also contributed to the financial crisis to develop in depth. Eco-financial nature, reflecting the internal and external financial elements of the value of the organic relationship between the United States is not just financial supervision and financial crisis, the crisis in the loan-to-time shown by the deterioration of social credit, lack of supervision of the market confusion, asymmetric information , The risk of moral hazard, and so is the ecological problems of the financial performance of major.
中文大意：
金融秩序与金融发展、金融创新失衡，金融监管缺位，是美国金融危机的重要原因。
此外，金融生态中的问题，也助长了金融危机进一步向纵深发展。金融生态本质上反映了金融内外部各要素之间有机的价值关系，美国金融危机不仅仅是金融监管的问题，次贷危机中所表现出的社会信用恶化、监管缺失、市场混乱、信息不对称、道德风险等，正是金融生态出现问题的重要表现。
希望对你有所帮助。
现代金融学的发展
一、金融问题中的不确定性研究
在21世纪以前的经济学研究中，研究者大多关注的是企业中的投入产出效率问题，由于当时资本市场化程度低，很少有人专门研究与资本决策有关的问题，尽管如此，还是有些研究成果对以后金融学的发展起到了很大的推动作用，其中最大的贡献是资金时间价值概念的提出。
随着金融市场的发展，以及人们对不确定性概念的认识，进入30年代以后产生了大量对金融决策问题的研究成果，同时这些成果又积极推进了金融市场的活跃与发展。在本文以下部分简要概述与评价了这一时期的重要研究成果。
（一）不确定性研究在资产定价领域中的应用
1.证券组合理论与资本资产定价模型
在整个金融分析的框架中，不确定性概念的引入是具有重大作用的。最早Kenes(1936)和Hicks(1939)提出了风险补偿的概念，认为由于金融产品中的不确定性的存在，应该对不同金融产品在利率中附加一定的风险补偿。随后，Von Neumann(1947)应用预期效用的概念提出了解决在不确定性条件下的决策选择的方法，在此基础上Markowiz(1952)发展起了证券组合理论，他认为投资者选择证券组合时关注的只是未来现金流的均值与方差。他假设投资者的预期效用符合二次分布或者是多项式分布。Markowiz的主要研究结论是在不确定的前提下，最优的投资决策是分散化持有。Tobin(1958)认为投资者出于自身流动性偏好的不同选择收益与风险的均衡。这进一步完善了证券组合选择理论的框架。
在资产定价领域另一著名的理论模型就是资本定价模型(CAPM)，Sharp(1994)和Lintner(1995)用公式简明地表述了资产组合的价值与无风险利率以及资产的风险水平之间的关系。Black(1972)推出了即使在不存在无风险资产的情况下，Sharp和CAPM公式仍然成立，只是无风险利率被包括整个市场上所有资产的证券组合的预期收益率代替。与CAPM模型同时代出现的资产定价模型还有Ross(1977)的套利定价模型(APT)和Lucas(1978)典型代理资产定价模型。
以CAPM为代表的资产定价模型，为资产定价提供了一个简洁的计算方法，并且得到了一些在实证方面的研究的支持(Fama and Macbeth,1973)，但是对现实中的一些异常现象仍然缺少有效的解释能力，Brennan(1989)认为CAPM是建立在所有投资者对投资的预期与风险都具有共同的估计与判断，并且所有投资者的效用函数一致的假设基础之上，这一假设与现实不一致，这是导致CAPM对一些现实问题缺少解释力的根本原因。以后正是对这些假设的质疑，推动了信息不对称概念的提出与研究。
2.市场有效性假说
市场有效性假说认为，在一个完全竞争市场中，不存在不对称信息与市场摩擦，影响未来平均收益的只是投资风险的不同。在20世纪60年代有大量研究工作者对市场有效性假说进行了检验，Fama(1973)通过对美国证券市场的实证检验，认为有效市场假说是成立的，但是很多研究人员发现了在市场中，存在着许多市场有效性假说或者CAPM模型解释不了的异常现象。例如，Basu(1977)发现资产的平均收益除了与CAPM中的β系数有关外，还与资产的价格盈利比率（P/E比率）有关，在相同β系数下，价格盈利比率高的股票（成长型股票）的市场价格好于价格盈利比率低的股票（价值型股票）；Benz(1981)发现股票的市场价格还与上市公司的规模有关；Stattman(1980)发现股票的价格与账面价值的比率（P/B比率）也是影响股票价格的重要因素。Fama和French(1993)在以上研究的基础上提出了三因素模型，即在影响资产价格的β因素外，加入了P/E比率和P/B比率因素。
另外，许多研究人员从时间序角度研究也发现了一些市场有效假说与CAPM解释不了的异常现象，其中最为著名的就是Pozeff和Kinney(1976)发现的所谓“一月效应”；他们发现在纽约证券市场的指数在一月期间的存在明显低于其他月份的现象；还有就是Cross(1973)和French(1980)发现存在类似的“星期一效应”，以后许多研究人员在世界范围内验证了这两种现象的存在。
对这些异常现象的解释，有效市场假说显得无能为力，有人曾经试图将“一月效应”解释为到年末税收流出的影响，但是在英国、澳大利亚等税收年度不在12月份的国家，仍然存在“一月效应”就无法解释了。有些学者从心理学的角度解释这些异常现象，例如，Dreman(1982)将股票价格的P/E比率效应解释为，由投资者总是过高估计具有高成长性股票的成长性，导致市场中具有高P/E比率的股票的价格被高估了，这是导致股票收益率低的原因。
3.连续时间模型
在资产定价理论中的另一个重要假设是：证券市场总是在连续过程中，在这一假设前提下，Merton(1969,1971)将CAPM发展为瞬时资本资产定价模型(ICAPM)，同样在信息对称、无摩擦的市场中，资产价格的变化符合Ito过程，在这种条件下，资产的价格与投资者的效用偏好无关。在随后的研究中Merton(1973)和Black(1973)应用以上连续时间模型成功地得到了期权定价公式，这一公式后来被大量的实证研究所证实，并且被广泛在实践中应用。
（二）不确定性研究在公司财务管理中的应用
金融分析研究的另外一个重要领域是公司财务管理，主要研究公司在投资决策中的有关负债与权益比例选择、公司的红利政策等问题。最早这方面的研究成果由Modigliani和Miller(1958)作出，他们的研究显示，在完全市场中（没有市场摩擦与信息不对称存在）公司的价值与公司的负债比率无关（M-M定理）。类似的研究结论还有，公司的价值与公司的利润分配政策无关。显而易见，这些研究结论与现实中的事实不符。依据M-M定理的结论，公司在利润分配时，由于派发现金红利会有现金流出，公司将更愿意选择股份回购的政策，而不是红利政策，而在现实中，许多公司更愿意选择分红而不是股份回购，这一现象被Black(1976)称为“公司红利的困惑(Dividend Puzzle)”，对此Miller(1977)所能给出的解释是，M-M定理的结论之所以与现实不同在于税收与所谓的破产成本对财务结构的影响，是由于一定的负债可以使公司达到税收减免的作用，另外由于对高负债率公司存在着破产的风险，所以负债率对公司股票价值存在影响，Miller以及其他的学者对这些财务问题做出的解释总体来说都不很令人满意，直到后来引入不对称信息以后，似乎才对这些问题的解释取得了突破。
二、金融中的不对称信息问题的研究
正如前文所述，对现实中的一些现象很难单纯用不确定性（风险）来得到满意的解释，正是在对这些问题的研究引起了人们对金融问题中的不对称信息的关注，加上在20世纪60年代以博弈论为代表的信息经济研究方法的突破，使得许多学者在对金融问题中的不对称信息的研究中取得了很多成果，特别是用不对称信息可以完美地解释许多有关财务结构方面的问题。以下仍然分两部分概述这方面的成果，首先是在财务决策方面的成果，接下来是在资产定价方面的成果。
（一）不对称信息在公司财务管理中的应用
1.红利信号模型
关于公司红利决策的困惑引起了许多学者的关注，除了以上提到的公司更愿意支付红利而不愿意将利润用于股份回购的异常现象之外，Lintner(1957)还发现公司在进行红利决策时，由于受累进税制的影响，更愿意使各年的红利平滑些，所以公司每年的红利波动要远远小于股票价值波动，有关税收减免的理论解释较为理想，并且在以后被许多学者用实证方法证实了这一现象的存在（例如：Fama and Babiak,1968）。但是税收效应并没有很好解释公司为什么更愿意支付红利的困惑。
最早Miller(1961)注意到红利可能是向投资者揭示公司发展前景的信号，但是直到Bhattacharya(1979)才应用博弈论方法建立起了红利模型，Bhattaeharya成为第一个将博弈论引入金融分析的学者，Bhattacharya认为公司的管理者对公司投资项目的前景与其他普通投资者相比具有信息方面的优势，管理者通过公司的尽可能高的红利向普通投资者传递信息，如果公司红利水平高意味着公司投资项目的未来前景好，而对于无法支付高额红利的公司将不得不向银行贷款，从而担负过高的财务成本。以后许多学者在此基础上对模型又进行了一个改造(Miller and Rock,1985;John and Williams,1985)。但是仍有学者质疑认为，按照以上模型认为只有在公司需要为新项目向市场融资时，才有积极性支付高水平的红利，但事实上模型的红利支付水平并不受公司是否有新项目的影响。也就是说，上面的信号模型不能很好解释红利的平滑性。为此，Kumar(t988)发展出了一个粗糙信号(Coarse Signaling)模型，其结论认为公司在一定的利润范围内会支付同样水平的红利，直到公司的利润水平超出了这一范围，公司管理者才会调整红利支付水平。红利信号模型的另外一个问题是，公司为什么愿意支付红利，而不是股票回购。Ofer和Thakor(1987),Barclay和Smith(1988)用逆向选择原理解释了这一现象，他们认为公司更愿意在市场上自己股票被低估时回购股票，所以回购股票行为向市场传达了股票价值被低估的信号，所以会引起股票价值的上涨，从而使公司支付了额外的成本，而用红利分配利润不存在这一逆向选择问题。
2.资本结构
正如上文提到的，公司资本结构问题的研究在引入不对称信息以前一直没有得到令人满意的结论。应用博弈论描述公司资本结构的决策过程，大大推动了对公司基本结构决策研究的发展。
最早Ross(1977)建立了一个公司负债决策的博弈模型，其中公司通过负债率向资本市场传递公司未来经营前景的信息，由于高负债率可能导致公司破产的风险加大，而一旦公司破产将为公司的经营者带来损失，所以只有公司管理者对公司未来的现金收益乐观时才会在资本结构决策时选择贷款，提高负债率。而前景乐观的公司提高负债率的决策是前景悲观的公司所无法模仿的，所以对资本市场来说，高负债率是公司发展前景乐观的信号。随后在Myers(1984)的模型中，认为如果管理者在公司项目发展需要融资时，如果管理者认为目前市场上自己公司股票价值被市场高估了，会选择通过发行股票的直接融资方式，而如果管理者认为公司股票价值被低估了，就会选择贷款等间接融资方式，所以说公司增加发行股票向资本市场传递的是公司目前股票价值被高估的信号。Myers认为经营者在面对新项目需要投资时首先选择的是用自身盈利积累完成投资，其次是选择贷款等间接融资方式，最后才会选择发行股票的融资方式，这被称之为“融资顺序理论(Pecking order theory of finance)”。
在金融分析中应用博弈论的不对称信息理论取得较大成绩的研究就是所谓的代理问题的研究，Jensen和Mecking(1976)指出公司中存在两类代理问题，其一是债权人与股东的代理矛盾，其二是股东与公司管理者的代理矛盾。债权人与股东间的矛盾表现在股东总是扩大公司投资风险，因为项目成功了超额收益全部是股东的，而如果公司经营失败，破产的成本由债权人与股东共同负担。Diamond(1989)通过研究认为，在长期重复博弈条件下，股东的声誉可以在一定程度改善股东和债权人间的矛盾。股东与管理者间的矛盾是由于股东不能有效控制管理者的经营行为，因而管理者会最大化自己的利益，可能会损害股东利益。
在80年代末与90年代，出现了有大量关于代理问题的研究成果，Hart和Moore(1989,1994,1998)研究发现当企业家计划投资新项目而需要向外融资时，与投资者签订贷款合同是最优合同，得到这一结论的关键在于虽然企业家与外部投资者在项目未来进展的各个时期都可以观察到项目的收益情况，但是第三方（例如：法官）无法观察到项目的收益，此时贷款合同是最优融资合同，并且Hart认为由于贷款人在企业家不能偿还贷款时可以控制公司的资产，所以企业家有积极性偿还贷款。
3.公司所有权控制市场
公司所有权控制市场的概念最早是由Manne(1965)提出的，他认为为了有效的配置资源，公司所有权控制市场的存在是必要的，现代资本市场的有效运转离不开公司所有权控制市场的存在。在公司所有权控制市场中所有权的转移方式是多样化的，包括：收购、兼并、股票的发行以及委托代理关系的变化等手段。在传统的完全竞争、无摩擦的资本市场假设下，很少考虑公司所有权转移对公司价值的影响，而事实上每次兼并收购活动都会引起公司股票价值的大幅波动。直到进入80年代以后非对称信息概念的引入，使得人们认识到了公司所有权控制市场对资本市场影响的内在机制。
Crossman和Harl(19803研究了在公司收购过程中存在所谓的“免费搭车问题(Free Rider Problem)”，他们认为当收购方发现一个目标公司的运营效率低下，而决定收购目标公司时，面对外部的标购，原有的股东知道收购者通过收购后公司在新的经营者经营下，效率会提高，所以会自发抵制收购，等待收购价格的升高，直到收购价格升高到在新经营者的经营水平下的合理的价格时，原有股东才会出售手中股票。考虑到收购方在收购过程中搜集信息、组织收购是有成本的，所以采用标购行为实际上为收购方带来了损失。Shleifer和Vishny(1986)认为，如果收购方在标购目标公司以前就已经持有了目标公司的一定股票，可以解决上述“搭车问题”的困惑，收购方可以用自己手中股票的增值弥补收购带来的损失。然而Shleifer和Vishny的结论并没有在实证中得到证实，反而Desai和Kim(1988)的实证结果认为大多数的收购方在标购前并没有持有目标公司的股票。
在收购行为研究方面的另外一个困惑就是收购行为往往导致股票价格的大幅上涨，例如：Jennings和Mazzeo(1993)发现收购发生时的收购人对目标公司的首次出价，大多数高于收购前10天的股票价格的20%。Fishman(1988)将这种现象解释为是由于有潜在竞争者随时会加入收购，较高的出价是为了阻止竞争者加入。
4.新股发行(IPO)
在1963年在由美国证券交易委员会组织的一项研究中，首次发现在新股上市后的短期存在着明显的超额回报的现象，以后许多学者在许多国家发现了这一现象，例如：Ibbotson和Ritter(1995)统计得出美国纽约证券市场1960-1992年发行新股的首日的超额回报是15.3%。在许多年中IPO现象成为挑战市场有效性假说的又一个证据。
对IPO现象最早的解释是由Rock(1986)作出的，Rock认为IPO现象实质是个逆向选择问题，新股上市时市场上存在着两类投资者，一类是具有信息优势的投资者，一类是不具信息优势的投资者，信息投资者只是在新股定价低于其真实价值时才购买，而当定价高于其真实价值时只有不具信息优势的投资者才会参加购买，所以平均来说，不具信息优势的投资者购入了较大比例的被过高定价的股票，为了在市场中留住不具信息优势的投资者，公司在初次发行新股时常常有意低定价。类似Rock对IPO超额回报问题的解释，许多研究人员给出了这一问题的其他合理解释，例如：Allen和Faulhaber(1989)以及Grinblatt和Hwang(1989)将新股发行低定价解释为公司未来前景良好的信号；Hughes和Thakor(1992)认为公司新股发行低定价是为了规避诉讼风险；Ruud(1993)认为新股上市后的短期高回报是由于承销商的价格稳定活动造成的。
在IPO领域中的另外一个难以解释的现象就是新股上市后长期表现不好。Ritter(1991)研究发现，在1975-1984年间发行的新股在发行后3年间的回报比正常股票的回报至少低15%。以后Loughran(1993,1995)再次证实了这一现象的存在。Shiller(1990)用所谓“主持人效应”解释新股长期回报不好的现象，他认为新股上市的初期承销商出于对自身声誉的考虑会创造短期超额需求的假象，随后随着承销商从市场的退出，导致了新股长期回报不佳的现象。
（二）不对称信息在资产定价领域中的应用
Grossman和stiglitz(1980)最早将非合作不对称信息的概念引入资产定价领域的研究中，建立了所谓资产定价的理性预期均衡理论，他们认为资本市场中的每个参与者都从市场价格的变化中获得信息（所谓的学习过程），并且每个参与者的行为不会对市场价格构成影响。在80年代初期这一理论成果主要用于解释公司财务方面的问题，直到Kyle(1985)以及Kyle和Milgrom(1985)研究做市商制度下的价格形成机制的成果出现以后，不对称信息对资产价格的影响才越来越多地引起人们关注，以后在Kyle Milgrom框架的基础上出现了大量的研究成果。由于在这一框架下的价格决定机制不同于Modigliani Miller的市场均衡机制，是通过研究具体市场条件下的资产价格形成机制，所以常常将这部分研究成果称为市场微观结构理论。
Kyle研究了在做市商制度下证券市场的价格形成机制，在Kyle的模型中，市场由三类参与者构成：风险中性的做市商、噪音交易者和信息交易者，噪音交易者出于自己的流动性需求进入市场交易，信息交易者根据自己的信息交易，为了最大化自己的利益，信息交易者选择自己在市场上的交易数量。与Kyle不同之处在于，Milgrom建立的序贯交易模型(Sequential Trade Model)中交易者每次交易的数量都是固定的，即每次都只能买入或卖出一个单位的资产，做市商根据交易指令的类型来设定买卖价差，在均衡条件下，由于有竞争做市商的存在，买入报价是做市商收到卖出指令时关于资产价值的条件期望值，卖出报价是做市商收到买入交易指令时关于资产价值的条件期望值，因而交易者的交易指令将促使做市商调整其买卖报价，这种调整从本质上是一种贝叶斯学习过程。
Easley和O'Hara(1987)在Milgrom模型的基础上考察了交易规模对做市商价格行为的影响，其结论是做市商的定价策略会依赖指令的规模，数量比较大的指令往往以比较差的价格成交。以后Easley和O'Hara(1992)又考察了交易时间对价格行为的影响，发现交易时间会影响价格，并且交易间隔影响交易价差的大小。
现代金融理论方法经过近一个世纪的发展，取得了许多重大突破，特别是进入80年代以后，越来越多的金融难题得到解释。但是由于金融市场的复杂性，至今对许多问题的解释还很难令人满意，例如：对P/E比率和P/B比率对资产价值的影响的现象至今还没有合理的解释，对IPO以及基金中的折价现象的研究结果也没有较为统一的认识，另外市场中是否存在信息操纵问题也是一个争论的焦点。对这些问题的研究与解释，将进一步推动金融理论的发展。
随着经济的全球化以及我国逐步开放金融业，我国的金融体系越来越成为世界金融体系不可分割的一部分。然而20世纪以来频繁发生的金融危机却明白无误地昭示着金融危机的危害性。尤其是对于我们这样一个大国而言，金融危机在某种意义上可能就是一个灾难性的结果。虽然我国迄今还未曾在发生金融危机，但是这并不意味着我国的经济结构和金融体系有多么健全，而更多地可归结为我国先前所处的封闭状态。事实上，国外近年来关于中国爆发金融危机的论调几乎就不曾停止过。比如尼古拉斯•拉迪就认为，中国的金融危机早已成熟，唯一缺乏的是引发危机全面爆发的导火索（吴传俯，2003）。更有《远东经济评论》2002年发表文章认为“中国金融系统在走向毁灭”。虽然这些观点各有其出发点，但是中国经济体系内部存在着许多诱发金融危机的因素却是不争的事实。因此，在金融开放已成为趋势的当前，从其他国家发生的金融危机中汲取经验，防范金融危机并且增强自身抵御金融危机的能力就更显得迫切而重要。
一、理论综述
关于金融危机，比较权威的定义是由戈德斯密斯（1982）给出的 ，是全部或大部分金融指标——短期利率、资产（资产、证券、房地产、土地）价格、商业破产数和金融机构倒闭数——的急剧、短暂和超周期的恶化。其特征是基于预期资产价格下降而大量抛出不动产或长期金融资产，换成货币。金融危机可以分为货币危机、债务危机、银行危机等类型。而近年来的金融危机越来越呈现出某种混合形式的危机。
（一）马克思的金融危机理论
马克思关于金融危机的理论是在批判李嘉图的“比例”理论、萨伊的“市场均衡法则”的基础上建立的。马克思指出，货币的出现使商品的买卖在时间上和空间上出现分离的可能性，结果导致货币与商品的转化过程出现不确定性，而货币作为支付手段的职能在客观上又会产生债务支付危机的可能性；因此，导致金融危机和经济危机的可能性的关键在于商品和货币各自不同的独立运动价值特性。而只要商品、货币存在，经济危机就不可避免，并且会首先表现为金融危机。
马克思进一步指出，“一旦劳动的社会性质表现为商品的货币存在，从而表现为一个处于现实生产之外的东西，独立的货币危机或作为现实危机尖锐化的货币危机，就是不可避免的。” 可见，马克思是将货币金融危机分为两种类型：伴随经济危机发生的货币金融危机和独立的货币金融危机。伴随经济危机的金融危机主要是以市场竞争、资本积累以及信用发展等因素为现实条件，而独立的货币金融危机则是金融系统内部紊乱的结果。同时马克思特别强调了银行信用在缓和和加剧金融危机中的作用。
总的来说，马克思认为金融危机是以生产过剩和金融过剩为条件，表现为企业和银行的流动性危机、债务支付危机，但是其本质上是货币危机。
（二）西方的金融危机理论
早期比较有影响的金融危机理论是由Fisher（1933）提出的债务－通货紧缩理论。Fisher认为，在经济扩张过程中，投资的增加主要是通过银行信贷来实现。这会引起货币增加，从而物价上涨；而物价上涨又有利于债务人，因此信贷会进一步扩大，直到“过度负债”状态，即流动资产不足以清偿到期的债务，结果引起连锁的债务－通货紧缩过程，而这个过程则往往是以广泛的破产而结束。在Fisher的理论基础上，Minsky（1963）提出“金融不稳定”理论，Tobin（1980）提出“银行体系关键”理论，Kindleberger（1978）提出“过度交易”理论， M.H.Wolfson（1996）年提出“资产价格下降”理论，各自从不同方面发展了Fisher的债务－通货紧缩理论。
70年代以后的金融危机爆发得越来越频繁，而且常常以独立于实际经济危机的形式而产生。在此基础上，金融危机理论也逐渐趋于成熟化。从70年代到90年代大致分为三个阶段。第一阶段的金融危机模型是由P.Krugman（1979）提出的，并由R.Flood和P.Garber加以完善和发展，认为宏观经济政策和汇率制度之间的不协调是导致金融危机的原因；第二阶段金融危机模型是由以M.Obstfeld（1994、1996）为代表，主要引入预期因素，对政府与私人之间进行动态博弈分析，强调金融危机由于预期因素存在的自促成性质以及经济基础变量对于发生金融危机的重要作用。1997年亚洲金融危机以后，金融危机理论发展至第三阶段。许多学者跳出货币政策、汇率体制、财政政策、公共政策等传统的宏观经济分析范围，开始从金融中介、不对称信息方面分析金融危机。其中有代表性的如Krugman(1998)提出的道德风险模型，强调金融中介的道德风险在导致过度风险投资既而形成资产泡沫化中所起的核心作用；流动性危机模型（J.Sachs，1998），侧重于从金融体系自身的不稳定性来解释金融危机形成的机理；“孪生危机”( Kaminsky & Reinhart, 1998 ) ，从实证方面研究银行业危机与货币危机之间固有的联系。
二、金融危机的国际经验与教训
从历史上看，早期比较典型的金融危机有荷兰的“郁金香狂热”、英格兰的南海泡沫、法国的密西西比泡沫以及美国1929年的大萧条等等。由于篇幅所限，本文仅回顾20世纪90年代以来所发生的重大金融危机，并试图从中找出导致金融危机发生的共同因素，以为我国预防金融危机提供借鉴。
（一）90年代一共发生了五次大的金融危机，根据时间顺序如下：
1.1992－1993年的欧洲货币危机
90年代初，两德合并。为了发展东部地区经济，德国于1992年6月16日将其贴现率提高至8.75％。结果马克汇率开始上升，从而引发欧洲汇率机制长达1年的动荡。金融风波接连爆发，英镑和意大利里拉被迫退出欧洲汇率机制。欧洲货币危机出现在欧洲经济货币一体化进程中。从表面上看，是由于德国单独提高贴现率所引起，但是其深层次原因是欧盟各成员国货币政策的不协调，从而从根本上违背了联合浮动汇率制的要求，而宏观经济政策的不协调又与欧盟内部各成员国经济发展的差异紧密相连。
2.1994－1995年的墨西哥金融危机。
1994年12月20日，墨西哥突然宣布比索对美元汇率的波动幅度将被扩大到15％，由于经济中的长期积累矛盾，此举触发市场信心危机，结果人们纷纷抛售比索，1995年初，比索贬值30％。随后股市也应声下跌。比索大幅贬值又引起输入的通货膨胀，这样，为了稳定货币，墨西哥大幅提高利率，结果国内需求减少，企业大量倒闭，失业剧增。在国际援助和墨西哥政府的努力下，墨西哥的金融危机在1995年以后开始缓解。墨西哥金融危机的主要原因有三：第一、债务规模庞大，结构失调；第二、经常项目持续逆差，结果储备资产不足，清偿能力下降；第三、僵硬的汇率机制不能适应经济发展的需要。
3.1997－1998年的亚洲金融危机
亚洲金融危机是泰国货币急剧贬值在亚洲地区形成的多米诺骨牌效应。这次金融危机所波及的范围之广、持续时间之长、影响之大都为历史罕见，不仅造成了东南亚国家的汇市、股市动荡，大批金融机构倒闭，失业增加，经济衰退，而且还蔓延到世界其它地区，对全球经济都造成了严重的影响。亚洲金融危机涉及到许多不同的国家，各国爆发危机的原因也有所区别。然而亚洲金融危机的发生决不是偶然的，不同国家存在着许多共同的诱发金融危机产生的因素，如宏观经济失衡，金融体系脆弱，资本市场开放与监控，货币可兑换与金融市场发育不协调等问题.
With the globalization of the economy and the gradual opening up of China's financial sector, China's financial system is the world's financial system has increasingly become an integral part. Since the 20th century, however frequent the financial crisis has clearly demonstrated the danger of a financial crisis. Especially for a big country like ours, the financial crisis may in a sense is a disastrous outcome. Although not yet in the event of financial crisis, but this does not mean that China's economic structure and how a sound financial system, and more can be attributed to China's closed earlier. In fact, in recent years, foreign financial crisis on China's argument almost never stopped. • For example, Nicholas Lardy on China's financial crisis is already mature, the only lacking is full-blown crisis of the fuse (down Wu, 2003). More, "Far Eastern Economic Review" published an article in 2002 that "China's financial system in the direction of destruction." Although these views have their starting point, but within the Chinese economy there are many factors that trigger the financial crisis, it is an undisputed fact. As a result, has become the trend of financial liberalization of the current, which occurred from other countries learn from the experience of the financial crisis and prevent financial crises and to strengthen its ability to withstand the financial crisis is all the more urgent and important.
I. Theory
On the financial crisis, the authority of the definition of comparison is by Goldsmith (1982) given that all or most of the financial indicators - short-term interest rates, assets (assets, securities, real estate, land) prices, the number of business bankruptcy and the closure of a number of financial institutions - the sharp, short and ultra-cycle deterioration. Its characteristics is based on the expected decline in asset prices and a large number of out of real estate or long-term financial assets into the currency. Financial crisis can be divided into currency crises, debt crises, banking crises, such as the type. In recent years more and more of the financial crisis showed a mixed form of crisis.
(A) Marx's theory of financial crisis
Marxist theory on the financial crisis in the Ricardian criticism of the "proportional" theory, say the "market equilibrium rule" based on the. Marx pointed out that the emergence of the currency of the sale of goods in time and space emerged the possibility of separation, resulting in the conversion of currency and commodity process uncertainty, and currency as a means of payment in the objective function of the debt will have to pay the possibility of a crisis; therefore, lead to a financial crisis and economic crisis lies in the possibility of their goods and monetary value of different characteristics of the independence movement. And so long as the commodity, currency exists, the economic crisis is inevitable, and will first be reflected in the financial crisis.
Marx further pointed out that "once the performance of the social nature of labor as a commodity currency exists, and thus the performance of the production of a reality other than in things, an independent monetary crisis or acute crisis, as the reality of the currency crisis is inevitable." Can be seen Marx is the monetary and financial crisis will be divided into two types: with the economic crisis occurred in the monetary and financial crisis and an independent monetary and financial crisis. With the economic crisis of the financial crisis is based on market competition, capital accumulation, as well as the development of factors such as credit for the actual conditions, and an independent monetary and financial crisis in the financial system is the result of internal disorder. At the same time, special emphasis on Marxism in easing bank credit and increased the role of the financial crisis.
In general, Marx believed that the financial crisis is overproduction and a surplus for the financial conditions, performance for the enterprise and banking liquidity crisis, debt payment crisis, but it is essentially a currency crisis.
(B) the Western theory of financial crisis
Comparison of influential early theory of the financial crisis by Fisher (1933) raised the debt - deflation theory. Fisher believes that the process of economic expansion, the increase in investment was mainly achieved through bank credit. This will cause an increase in currency in order to price increases; and inflation and in favor of the debtor, the credit will be further expanded, until the "over-indebtedness", and that is not enough liquid assets maturing debt obligations outstanding, the result was a chain reaction of debt - deflation process and this process is often the end of a wide range of bankruptcy. In the basis of Fisher's theory, Minsky (1963) put forward the "financial instability" theory, Tobin (1980) that "the key to the banking system" theory, Kindleberger (1978) that "excessive trading" theory, MHWolfson (1996) put forward " decline in asset prices "theory, the different aspects of their development from the Fisher's debt - deflation theory.
70 since the outbreak of the financial crisis are becoming more and more frequent, and often independent of the actual form of the economic crisis arising. On this basis, the theory of financial crises are becoming more and more mature. From 70's to 90's roughly divided into three stages. The financial crisis in the first phase of the model is by P. Krugman (1979) put forward by R. Flood and P. Garber and development to perfect that the macroeconomic policies and exchange rate system is the lack of coordination between the causes of financial crisis ; the second phase of financial crisis, the model is by M. Obstfeld (1994,1996), represented mainly the introduction of the expected factors, between the Government and the private sector dynamic game analysis, stressing that the financial crisis as a result of factors expected to contribute to the nature of the self as well as economic the basis of variables for the occurrence of the important role of the financial crisis. The 1997 Asian financial crisis, the financial crisis to the third phase of theoretical development. Many scholars out of monetary policy, exchange rate system, fiscal policy, public policy, such as the traditional scope of macroeconomic analysis, from the financial intermediation, asymmetric information analysis of the financial crisis. One representative, such as Krugman (1998) raised the risk of moral hazard model, to emphasize the moral hazard of financial intermediaries in the investment subsequently led to the formation of excessive risk of asset bubbles in the central role; liquidity crisis model (J. Sachs, 1998) , focusing on its own financial system from instability to explain the formation mechanism of the financial crisis; "twin crises" (Kaminsky & Reinhart, 1998), empirical research from the banking crisis and currency crisis in the inherent link between.
Second, the financial crisis and lessons of international experience
Historically, typical of early financial crisis, the Netherlands, "Tulip Fever", the South Sea Bubble in England, France and the United States of the Mississippi bubble in 1929 and so on of the Great Depression. Due to limited space, this article only to recall the 20th century have occurred since the 90's a major financial crisis, and attempts to find financial crisis led to the common factors that prevent financial crises in our country for reference.
(A) a total of 90 occurred during the five major financial crisis, according to chronological order as follows:
1.1992-1993 in the European currency crisis
The early 90s, the two Germanys merged. In order to develop the eastern part of the regional economy, Germany in June 16, 1992 to raise its discount rate to 8.75 percent. The results mark the exchange rate began to rise, causing the European exchange rate mechanism of the instability as long as 1 year. The outbreak of the financial crisis after another, pound sterling and Italian lira were forced to withdraw from the European Exchange Rate Mechanism. European currency crisis in the European Economic and Monetary integration process. On the surface, is due to Germany to raise the discount rate arising from a separate, but their deep-seated reason is that EU member states co-ordination of monetary policy, thereby fundamentally contrary to the Joint floating exchange rate system requirements, and macroeconomic policy does not Coordination with EU Member States the difference between economic development are closely linked.
2.1994-1995 financial crisis in Mexico.
December 20, 1994, the Mexican peso against the U.S. dollar suddenly announced fluctuations of the exchange rate will be extended to 15%, as the economy's long-term accumulation of contradictions in the market would trigger a crisis of confidence, the result of people selling their pesos, early in 1995, the peso devaluation 30%. Subsequent stock market drop. Substantial depreciation of the peso and the inflation caused by input, so that in order to stabilize the currency, a substantial increase in Mexican interest rates, the result of reduced domestic demand, a large number of enterprises closed down, unemployment increased. In the international assistance and the efforts of the Government of Mexico, Mexico's financial crisis began to ease after 1995. Mexico's financial crisis for three main reasons: First, the scale of debt, structural imbalance; Secondly, the current account deficit continued, resulting in lack of reserve assets, decreased liquidity; Third, the rigid exchange rate regime can not adapt to the needs of economic development.
3.1997-1998 years of the Asian financial crisis
The Asian financial crisis was a sharp devaluation of the Thai currency in Asia, the formation of a domino effect. The financial crisis affected the scope and duration, the effects of history are rare, not only in Southeast Asian countries resulted in the currency markets, the stock market turbulence, a large number of financial institutions collapse, rising unemployment, economic recession, but also spread to the world other regions of the global economy has had a significant impact. The Asian financial crisis, involving many different countries, the reasons for the outbreak of the crisis also differ. However, the occurrence of the Asian financial crisis is not accidental, there are many different countries induced by common factors arising from the financial crisis, such as macro-economic imbalances, the fragile financial system, capital market openness and control, currency convertibility and financial market development and other non-conforming issue
