【正文】 does not exist, and in fact bee a creditor of the business owners. Reality shows that no pany is 100% liability, so the scholars of the MM theory and the theory of eating Miller considerable skepticism. Is generally believed that these theories of the derivation itself is not wrong, the problem from the theoretical most aggressive of a theoretical argument is that MM does not take bankruptcy costs and agency costs.The Tradeoff theoryTradeoff theory is used in reference to Myers, but this formulation is not appropriate, because the broad sense, the history of the way of capital structure theory is a tradeoff theory of history, the main elements are the costs of capital structure research weigh the issues and interests. So not used to weigh a specific school, we have to weigh the meaning of this is theoretical orientation: the 20th century, the mid70s to form the academic theory of capital structure on the general point of view, the view is that the optimal capital structure of enterprises in the tax benefits and liabilities of bankruptcy cost tradeoff between the present value. So tradeoff theory can also be known as the theory of optimal capital structure.After the development of tradeoff theory for the posttradeoff theory, the theory of the cost of the liabilities from the further expansion of bankruptcy costs to the agency costs, financial distress costs and nontax loss of interest, etc. At the same time, then the tax benefits extended to the interests of nontax liabilities In fact, is the expansion of the costs and benefits of what is contained in the optimal capital structure of panies as a tax benefit in a variety of cost and liabilities related to the balance between the cost.The introduction of asymmetric information theory of the new capital structureNew capital structure theory to a focus only on antitax, bankruptcy and other external factors for most enterprises the impact of capital structure theory, trying to asymmetric information theory of the signal, motivation, incentives such as the concept of from the enterprise of internal factors to start on the issue of capital structure analysis. So as to balance the capital structure problem into a structure or system design problems, thus the capital structure to the theoretical issues opened up new research directions, provide a new interpretation, so that the capital structure theory since then have entered a new stage of development, we call The theory of capital structure for the new.New theory of capital structure is characterized by one of the largest recognized the asymmetry of information in the capital structure decision in the role, Meyers, and theoretical perspectives Meki Sharif：In the study the role of agency costs and capital structure to the Department of Asymmetric Information regard, Myers has been the most influential one of the scholars. Meyers and Meki Sharif pointed out that if investors do not like people do party vendors and internal value of the assets of the manufacturers of the wellinformed information, then the equity market may be priced incorrectly. If panies need to issue stock to finance new projects, if the stock price is too low as a result of new investors to the extent that the new project than NPV (net present value that is) more of the value of existing shareholders will result in a net loss of . In this case, even if NPV is positive, the project will be rejected. If manufacturers can take advantage of its market value so do not underestimate the securities financing for new projects，Lack of such investment will be avoided. Therefore, in this case, with more preference shares pared to firms inhouse funds, and even the risk of not too much debt than equity superior. Because of this, Myers pointed out that the capital structure for the new panies will be subject to the wishes of the financing of investmentdriven, first internal financing, then the lowrisk debt, and the equity only as a last resort.附 錄2關于稅收對資本結構的影響——MM定理 1．存在公司所得稅條件下的MM定理在存在公司所得稅的情況下，公司的價值隨著負債增加而相應增加，負債越多，公司價值越大。實際情況一般并不支持這一結論，于是絕大部分人認為還存在著其他的市場不完善性，那就是因負債過多而引起的財務虧空概率和破產風險壓低了公司的債務比。2．存在個人所得稅條件下的MM定理 米勒指出，按照1986年以前的美國稅法，個人由債券和股票中得來的收入所付的稅率是不同的。但是股票收益中的資本收益（買賣股票的價差）的實際稅率低于股票和債券的利息收入稅率，因為股票資本收益中最初60%的長期資本收益是免稅的，而且只有在資本收益切實實現(xiàn)，即賣出股票后才付稅，潛在的未實現(xiàn)資本收益是免稅的。這顯然會影響個人的投資決策。但從邏輯上講，100%的負債就不存在股東了，債權人變成了實際上的企業(yè)所有者。一般認為這些理論本身的推導并沒有錯誤，問題來自理論的假設。 權衡理論的觀點 權衡理論是沿用梅耶斯的提法，但這一提法并不貼切，因為從廣義上講，資本結構理論史就是一部“權衡”理論史，主要內容都是研究資本結構的成本與利益的權衡問題。所以說權衡理論也可稱作最優(yōu)資本結構理論。引入不對稱信息的新資本結構理論 新資本結構理論者一反只注重對稅收、破產等外部因素對企業(yè)最有資本結構理論的影響，試圖通過信息不對稱理論中的信號、動機、激勵等概念，從企業(yè)內部因素來展開對資本結構問題的分析。新資本結構理論的一個最大的特點就是認識到了不對稱信息在資本結構決定中所起的作用，梅耶斯和邁基里夫提出：在研究代理成本的作用和資本結構對稱信息方面，梅耶斯一直是最有影響力的學者之一。如果廠商需要以發(fā)行股票為新項目融資，若由于股票價格過低以至于是新投資者能夠從新項目中獲得比NPV（即凈現(xiàn)值）更多的價值，便將導致現(xiàn)有股東的一個凈損失。如果廠商能夠利用其價值沒被市場如此低估的證券為新項目籌資，則這種投資不足就會被避免。由此，梅耶斯指出資本結構將受到廠商為新投資融資的愿望驅使，先是內部融資，然后是低風險債務，而把股權只當作最后一