行业竞争、管理层投资决策与公司增长/清算期权价值
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摘要
本文首先考察了行业竞争对公司管理层投资决策的影响,结果显示,行业竞争显著增加了管理层的投资灵活性,并且有助于改善公司的投资效率。另外,本文还从实物期权的角度考察了行业竞争对公司增长和清算期权价值的影响。结果表明,行业竞争显著增加了公司增长和清算期权的价值。这些发现意味着,行业竞争作为公司经营环境的重要组成部分,影响了公司管理层的投资决策行为,并且这种影响最终体现在公司价值之中。
This paper investigates how the industry competition influences the decisionmaking of managerial investment,and the equity value of growth and put options.Our results show that the intense industry competition increases the sensitivity of investment to growth opportunity,and improves the investment efficiency.In addition,we observe that the intense industry competition increases the equity value of growth and put options.Overall,these findings demonstrate that the industry competition,as an important ingredient of the companies'operating environments,has a significant impact on investment and equity value of a company.
This paper investigates how the industry competition influences the decisionmaking of managerial investment,and the equity value of growth and put options.Our results show that the intense industry competition increases the sensitivity of investment to growth opportunity,and improves the investment efficiency.In addition,we observe that the intense industry competition increases the equity value of growth and put options.Overall,these findings demonstrate that the industry competition,as an important ingredient of the companies'operating environments,has a significant impact on investment and equity value of a company.
引文
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[3]Baker,M.,J.Stein,and J.Wurgler,“When Does the Market Matter?Stock Prices and the Investment of Equity-Dependent Firms”,Quarterly Journal of Economics,2003,118(3),969—1005.
[4]Biddle,G.,P.Chen,and G.Zhang,“When Capital Follows Profitability:Non-linear Residual Income Dynamics”,Review of Accounting Studies,2001,6(2),229—265.
[5]Biddle,G.,G.Hilary,and R.Verdi,“How Does Financial Reporting Quality Relate to Investments Efficiency?”,Journal of Accounting and Economics,2009,48(2),112—131.
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[7]Burgstahler,D.,and I.Dichev,“Earnings,Adaptation and Equity Value”,The Accounting Review,1997,72(2),187—215.
[8]Chen,C.,P.Chen,and Q.Jin,“Economic Freedom,Managerial Flexibility and Equity Value:A Cross-Country Study”,Working Paper,Hong Kong University of Science and Technology,2012.
[9]Chen,F.,O.Hope,Q.Li,and X.Wang,“Financial Reporting Quality and Investment Efficiency of Private Firms in Emerging Markets”,The Accounting Review,2011,86(4),1255—1288.
[10]陈运森、谢德仁,“网络位置、独立董事治理与投资效率”,《管理世界》,2011年第7期,第113—127页。
[11]Darrough,M.,and N.Stoughton,“Financial Disclosure Policy in an Entry Game”,Journal of Accounting and Economics,1990,12(1),219—243.
[12]Dechow,P.,“Accounting Earnings and Cash Flows as Measures of Firm Performance:The Role of Accounting Accruals”,Journal of Accounting and Economics,1994,18(1),3—42.
[13]Dechow,P.,S.Kothari.,and R.Watts,“The Relation Between Earnings and Cash Flows”,Journal of Accounting and Economics,1998,25(2),133—168.
[14]Easton,P.,and T.Harris,“Earnings as an Explanatory Variable for Returns”,Journal of Accounting Research,1991,29(1),19—36.
[15]樊纲、王小鲁、朱恒鹏,《中国市场化指数:各地区市场化相对进程2011年报告》。北京:经济科学出版社,2011年。
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[17]方军雄,“市场化进程与资本配置效率的改善”,《经济研究》,2006年第5期,第50—61页。
[18]Fee,E.,and C.Hadlock,“Management Turnover and Product Market Competition:Empirical Evidence from the U.S.Newspaper Industry”,Journal of Business,2000,73(2),205—243.
[19]Hart,O.,“The Market Mechanism as an Incentive Scheme”,The Bell Journal of Economics,1983,14(2),366—382.
[20]Hayashi,F.,“Tobin's Marginal q and Average q:A Neoclassical Interpretation”,Econometrica,1982,50(1),213—224.
[21]Hermalin,B.,“The Effects of Competition on Executive Behavior”,The RAND Journal of Economics,1992,23(3),350—365.
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[23]Holmstrom,B.,“Moral Hazard in Terms”,The Bell Journal of Economics,1982,13(2),324—340.
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[26]靳庆鲁、孔祥、侯青川,“货币政策、民营企业投资效率与公司期权价值”,《经济研究》,2012年第5期,第96—106页。
[27]靳庆鲁、薛爽、郭春生,“市场化进程影响公司的增长与清算价值吗?”,《经济学》(季刊),2010年第9卷第4期,第1485—1504页。
[28]Karuna,C.,“Industry Product Market Competition and Managerial Incentives”,Journal of Accounting and Economics,2007,43(2),275—297.
[29]Larcker,D.,and T.Rusticus,“On the Use of Instrumental Variables in Accounting Research”,Journal of Accounting and Economics,2010,49(3),186—205.
[30]Leibenstein,H.,“Allocative Efficiency vs.X-Efficiency”,American Economic Review,1966,56(3),392—415.
[31]Li,X.,“The Impacts of Product Market Competition on the Quantity and Quality of Voluntary Disclosures”,Review of Accounting Studies,2010,15(3),663—711.
[32]刘凤委、孙铮、李增泉,“政府干预、行业竞争与薪酬契约——来自国有上市公司的经验证据”,《管理世界》,2007年第9期,第76—84页。
[33]刘志彪、姜付秀、卢二坡,“资本结构与产品市场竞争强度”,《经济研究》,2003年第7期,第60—67页。
[34]Liu,Q.,Y.Zheng,and Y.Zhu,“The Evolution and Consequence of Chinese Pyramids”,Working Paper,The University of Hong Kong,2011.
[35]Machlup,F.,“Theories of the Firm:Marginalist,Behavioral,Managerial”,American Economic Review,1967,57(1),1—33.
[36]Mclean,D.,T.Zhang,and M.Zhao,“Why Does the Law Matter?Investor Protection and Its Effects on Investment,Finance,and Growth”,Journal of Finance,2012,67(1),313—350.
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[38]Myers,S.,and N.Majluf,“Corporate Financing and Investment Decisions When Firms Have Information that Investors Do Not Have”,Journal of Financial Economics,1984,13(2),187—221.
[39]Nalebuff,B.,and J.Stiglitz,“Information,Competition,and Markets”,American Economic Review,1983,73(2),278—283.
[40]Nickell,S.,“Competition and Corporate Performance”,Journal of Political Economy,1996,104(4),724—746.
[41]Ohlson,J.,“Earnings,Book Values,and Dividends in Equity Valuation”,Contemporary Accounting Research,1995,11(2),661—687.
[42]Petersen,M.,“Estimating Standard Errors in Finance Panel Data Sets:Comparing Approaches”,Review of Financial Studies,2009,22(1),435—480.
[43]Raddatz,C.,“Liquidity Needs and Vulnerability to Financial Underdevelopment”,Journal of Financial Economics,2006,80(3),677—722.
[44]Raith,M.,“Competition,Risk and Managerial Incentives”,American Economic Review,2003,93(4),1425—1436.
[45]Richardson,S.,“Over-investment of Free Cash Flow”,Review of Accounting Studies,2006,11(2),159—189.
[46]Scharfstein,D.,“Product Market Competition and Managerial Slack”,The RAND Journal of Economics,1988,19(1),147—155.
[47]Schmidt,K.,“Managerial Incentives and Product Market Competition”,Review of Economic Studies,1997,64(2),191—213.
[48]Stigler,G.,“The Economics of Scale”,Journal of Law and Economics,1958,1(1),54—71.
[49]Tobin,J.,“A General Equilibrium Approach to Monetary Theory”,Journal of Money,Credit and Banking,1969,1(1),15—29.
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[51]White,H.,“A Heteroskedasticity-consistent Covariance Matrix Estimator and a Direct Test for Heteroskedasticity”,Econometrica,1980,48(4),817—838.
[52]夏立军、方轶强,“政府控制、治理环境与公司价值——来自中国证券市场的经验证据”,《经济研究》,2005年第5期,第40—51页。
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1以往的大部分估值模型均假定公司价值是会计信息的线性函数(Easton and Harris,1991;Ohlson,1995),然而与现实情况更为吻合的是,当经营比较成功时,公司可以选择按现有的商业技术来组织现有资源或扩大再生产;当经营比较失败时,公司可以选择改变现有资源的用途,将资本转移到回报率较高的其他领域。事实上这种决策恰好体现了公司管理层的能力,反映了管理层在公司投资决策中的作用。
2引入投资动态假定(即遵循资本逐利的经济规律)是Zhang(2000)实物期权价值模型的关键,亦是推演出公司权益价值与净利润和净资产之间凸增关系(即增长/清算期权价值)的前提假设之一。
3由于借鉴Li(2010)的衡量方法,并采用主成分分析法后得到的三个主分量均为标准化后的变量。为提高变量之间的可比性,类似地,我们也对HHI指数进行标准化,然后构造出HHI-COMP变量。当然,采用原始的HHI指数分析得到的结果与本文类似。
4在区分投资不足和投资过度时,Richardson(2006)的划分方法忽略了公司存在适度投资问题,当模型回归残差在0附近时受模型的偏误影响较大,故本文主要采用Biddle et al.(2009)的方法来划分。在稳健性检验部分,我们亦采用了Richardson(2006)的划分方法,发现主要结论不变。
5本文之所以采用分组而不是交互项的方法,是因为模型同时加入过多的交互项,会使得模型的方差膨胀因子(VIF)过大,导致严重的共线性问题。
6此外,根据匿名审稿人的建议,本文还采用了Fama-Macbeth Newey-West的调整方法对回归标准误进行修正,发现本文的研究结论没有发生实质性的变化。
7根据匿名审稿人的建议,本文还在模型中控制了政治关系和股权结构的影响。由于上市公司自2003年起才开始披露较为完整的控股关系图,限于数据的可获得性,本文仅将该部分作为稳健性测试。参照Fan et al.(2007),Liu et al.(2011)等的研究,我们用公司董事长或总经理是否正在或者曾在中央政府、地方政府或者军队任职来衡量政治关系;分别用公司是否存在金字塔结构、公司层级以及两权分离程度来衡量股权结构。回归结果显示,EXIST-COMP和PROFIT-COMP系数仍显著为负,而HHI-COMP(PROFIT-COMP)系数在投资不足(投资过度)组仍为负但不显著。总体来看,控制公司政治关系和股权结构特征后,本文假说2仍然成立。
8参照Karuna(2007)的定义:产品的差异化,等于某一年度某一行业内所有上市公司营业收入总和除以营业成本总和;市场规模,等于某一年度某一行业内所有上市公司销售收入之和的自然对数;进入成本,等于某一年度某一行业内所有上市公司加权平均“固定资产、无形资产等净额”的自然对数,其中权重为各上市公司的市场占有率。与前文一致,我们在行业层面对三个指标进行了标准化处理。
9 Sargan检验结果显示,检验统计量(Score Chi2)在10%的置信水平上不能拒绝“所有工具变量均为外生”的原假设;在2SLS估计中第一阶段回归方程中工具变量的partial-R2均大于0.35,且对应的partialF值均大于100,表明工具变量与内生变量具有很高的相关性。满足工具变量有效性的两个条件。Hausman检验显示,借鉴Li(2010)方法衡量行业竞争程度时Wu-Hausman F统计量为1.858,在10%的置信水平上拒绝“原模型所有解释变量均为外生”的原假设,因而采用2SLS是必要的;而采用HHI指数衡量行业竞争时Wu-Hausman F统计量为0.907(P值为0.404),统计上不显著,意味着此处采用OLS也是有效的。
10 这里与Biddle et al.(2009)和Chen et al.(2011)的原始模型稍微不同的是,他们进行分年度分行业回归估计,而本文选择将行业特征作为哑变量在模型中加以控制并分年度回归。主要是由于本文重点考察的是行业层面的竞争因素对行业间投资效率差异的影响,如果采用分年度分行业回归,将消除行业间投资效率的差异,导致本文假说无法得到有效的检验。
11非常感谢匿名审稿人的建议,本文进一步从行业-年度层面重新检验研究假说。具体:第一,我们将公司-年度数据合成为行业-年度数据,共得到234个行业年度观测值;第二,采用Richardson(2006)模型以这些行业-年度观测值为样本进行回归并估计得残差;第三,参照Biddle et al.(2009)方法将行业-年度残差区分为投资不足和投资过度;第四,在行业-年度层面上进行投资效率的回归分析。回归结果显示,除了在投资过度组PROFIT-COMP的回归系数变得不再显著外,其余结论不受影响。
[2]Ali,A.,S.Klasa,and E.Yeung,“The Limitations of Industry Concentration Measures Constructed with Compustat Data:Implications for Finance Research”,Review of Financial Studies,2009,22(10),3839—3871.
[3]Baker,M.,J.Stein,and J.Wurgler,“When Does the Market Matter?Stock Prices and the Investment of Equity-Dependent Firms”,Quarterly Journal of Economics,2003,118(3),969—1005.
[4]Biddle,G.,P.Chen,and G.Zhang,“When Capital Follows Profitability:Non-linear Residual Income Dynamics”,Review of Accounting Studies,2001,6(2),229—265.
[5]Biddle,G.,G.Hilary,and R.Verdi,“How Does Financial Reporting Quality Relate to Investments Efficiency?”,Journal of Accounting and Economics,2009,48(2),112—131.
[6]Bresnahan,T.,“Chapter 17Empirical Studies of Industries with Market Power”,Handbook of Industrial Organization,1989,2,1011—1057.
[7]Burgstahler,D.,and I.Dichev,“Earnings,Adaptation and Equity Value”,The Accounting Review,1997,72(2),187—215.
[8]Chen,C.,P.Chen,and Q.Jin,“Economic Freedom,Managerial Flexibility and Equity Value:A Cross-Country Study”,Working Paper,Hong Kong University of Science and Technology,2012.
[9]Chen,F.,O.Hope,Q.Li,and X.Wang,“Financial Reporting Quality and Investment Efficiency of Private Firms in Emerging Markets”,The Accounting Review,2011,86(4),1255—1288.
[10]陈运森、谢德仁,“网络位置、独立董事治理与投资效率”,《管理世界》,2011年第7期,第113—127页。
[11]Darrough,M.,and N.Stoughton,“Financial Disclosure Policy in an Entry Game”,Journal of Accounting and Economics,1990,12(1),219—243.
[12]Dechow,P.,“Accounting Earnings and Cash Flows as Measures of Firm Performance:The Role of Accounting Accruals”,Journal of Accounting and Economics,1994,18(1),3—42.
[13]Dechow,P.,S.Kothari.,and R.Watts,“The Relation Between Earnings and Cash Flows”,Journal of Accounting and Economics,1998,25(2),133—168.
[14]Easton,P.,and T.Harris,“Earnings as an Explanatory Variable for Returns”,Journal of Accounting Research,1991,29(1),19—36.
[15]樊纲、王小鲁、朱恒鹏,《中国市场化指数:各地区市场化相对进程2011年报告》。北京:经济科学出版社,2011年。
[16]Fan,J.,T.Wong,and T.Zhang,“Organizational Structure as a Decentralization Device:Evidence from Corporate Pyramids”,Working Paper,The Chinese University of Hong Kong,2007.
[17]方军雄,“市场化进程与资本配置效率的改善”,《经济研究》,2006年第5期,第50—61页。
[18]Fee,E.,and C.Hadlock,“Management Turnover and Product Market Competition:Empirical Evidence from the U.S.Newspaper Industry”,Journal of Business,2000,73(2),205—243.
[19]Hart,O.,“The Market Mechanism as an Incentive Scheme”,The Bell Journal of Economics,1983,14(2),366—382.
[20]Hayashi,F.,“Tobin's Marginal q and Average q:A Neoclassical Interpretation”,Econometrica,1982,50(1),213—224.
[21]Hermalin,B.,“The Effects of Competition on Executive Behavior”,The RAND Journal of Economics,1992,23(3),350—365.
[22]Hubbard,R.,and D.Palia,“Executive Pay and Performance:Evidence from the U.S.Banking Industry”,Journal of Financial Economics,1995,39(1),105—130.
[23]Holmstrom,B.,“Moral Hazard in Terms”,The Bell Journal of Economics,1982,13(2),324—340.
[24]Jensen,M.,and W.Meckling,“Theory of the Firm:Managerial Behavior,Agency Costs,and Ownership Structure”,Journal of Financial Economics,1976,3(4),305—360.
[25]姜付秀、刘志彪,“行业特征、资本结构与产品市场竞争”,《管理世界》,2005年第10期,第74—81页。
[26]靳庆鲁、孔祥、侯青川,“货币政策、民营企业投资效率与公司期权价值”,《经济研究》,2012年第5期,第96—106页。
[27]靳庆鲁、薛爽、郭春生,“市场化进程影响公司的增长与清算价值吗?”,《经济学》(季刊),2010年第9卷第4期,第1485—1504页。
[28]Karuna,C.,“Industry Product Market Competition and Managerial Incentives”,Journal of Accounting and Economics,2007,43(2),275—297.
[29]Larcker,D.,and T.Rusticus,“On the Use of Instrumental Variables in Accounting Research”,Journal of Accounting and Economics,2010,49(3),186—205.
[30]Leibenstein,H.,“Allocative Efficiency vs.X-Efficiency”,American Economic Review,1966,56(3),392—415.
[31]Li,X.,“The Impacts of Product Market Competition on the Quantity and Quality of Voluntary Disclosures”,Review of Accounting Studies,2010,15(3),663—711.
[32]刘凤委、孙铮、李增泉,“政府干预、行业竞争与薪酬契约——来自国有上市公司的经验证据”,《管理世界》,2007年第9期,第76—84页。
[33]刘志彪、姜付秀、卢二坡,“资本结构与产品市场竞争强度”,《经济研究》,2003年第7期,第60—67页。
[34]Liu,Q.,Y.Zheng,and Y.Zhu,“The Evolution and Consequence of Chinese Pyramids”,Working Paper,The University of Hong Kong,2011.
[35]Machlup,F.,“Theories of the Firm:Marginalist,Behavioral,Managerial”,American Economic Review,1967,57(1),1—33.
[36]Mclean,D.,T.Zhang,and M.Zhao,“Why Does the Law Matter?Investor Protection and Its Effects on Investment,Finance,and Growth”,Journal of Finance,2012,67(1),313—350.
[37]Modigliani,F.,and M.Miller,“The Cost of Capital,Corporation Finance and the Theory of Investment”,American Economic Review,1958,48(3),261—297.
[38]Myers,S.,and N.Majluf,“Corporate Financing and Investment Decisions When Firms Have Information that Investors Do Not Have”,Journal of Financial Economics,1984,13(2),187—221.
[39]Nalebuff,B.,and J.Stiglitz,“Information,Competition,and Markets”,American Economic Review,1983,73(2),278—283.
[40]Nickell,S.,“Competition and Corporate Performance”,Journal of Political Economy,1996,104(4),724—746.
[41]Ohlson,J.,“Earnings,Book Values,and Dividends in Equity Valuation”,Contemporary Accounting Research,1995,11(2),661—687.
[42]Petersen,M.,“Estimating Standard Errors in Finance Panel Data Sets:Comparing Approaches”,Review of Financial Studies,2009,22(1),435—480.
[43]Raddatz,C.,“Liquidity Needs and Vulnerability to Financial Underdevelopment”,Journal of Financial Economics,2006,80(3),677—722.
[44]Raith,M.,“Competition,Risk and Managerial Incentives”,American Economic Review,2003,93(4),1425—1436.
[45]Richardson,S.,“Over-investment of Free Cash Flow”,Review of Accounting Studies,2006,11(2),159—189.
[46]Scharfstein,D.,“Product Market Competition and Managerial Slack”,The RAND Journal of Economics,1988,19(1),147—155.
[47]Schmidt,K.,“Managerial Incentives and Product Market Competition”,Review of Economic Studies,1997,64(2),191—213.
[48]Stigler,G.,“The Economics of Scale”,Journal of Law and Economics,1958,1(1),54—71.
[49]Tobin,J.,“A General Equilibrium Approach to Monetary Theory”,Journal of Money,Credit and Banking,1969,1(1),15—29.
[50]魏明海、柳建华,“国企分红、治理因素与过度投资”,《管理世界》,2007年第9期,第88—95页。
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1以往的大部分估值模型均假定公司价值是会计信息的线性函数(Easton and Harris,1991;Ohlson,1995),然而与现实情况更为吻合的是,当经营比较成功时,公司可以选择按现有的商业技术来组织现有资源或扩大再生产;当经营比较失败时,公司可以选择改变现有资源的用途,将资本转移到回报率较高的其他领域。事实上这种决策恰好体现了公司管理层的能力,反映了管理层在公司投资决策中的作用。
2引入投资动态假定(即遵循资本逐利的经济规律)是Zhang(2000)实物期权价值模型的关键,亦是推演出公司权益价值与净利润和净资产之间凸增关系(即增长/清算期权价值)的前提假设之一。
3由于借鉴Li(2010)的衡量方法,并采用主成分分析法后得到的三个主分量均为标准化后的变量。为提高变量之间的可比性,类似地,我们也对HHI指数进行标准化,然后构造出HHI-COMP变量。当然,采用原始的HHI指数分析得到的结果与本文类似。
4在区分投资不足和投资过度时,Richardson(2006)的划分方法忽略了公司存在适度投资问题,当模型回归残差在0附近时受模型的偏误影响较大,故本文主要采用Biddle et al.(2009)的方法来划分。在稳健性检验部分,我们亦采用了Richardson(2006)的划分方法,发现主要结论不变。
5本文之所以采用分组而不是交互项的方法,是因为模型同时加入过多的交互项,会使得模型的方差膨胀因子(VIF)过大,导致严重的共线性问题。
6此外,根据匿名审稿人的建议,本文还采用了Fama-Macbeth Newey-West的调整方法对回归标准误进行修正,发现本文的研究结论没有发生实质性的变化。
7根据匿名审稿人的建议,本文还在模型中控制了政治关系和股权结构的影响。由于上市公司自2003年起才开始披露较为完整的控股关系图,限于数据的可获得性,本文仅将该部分作为稳健性测试。参照Fan et al.(2007),Liu et al.(2011)等的研究,我们用公司董事长或总经理是否正在或者曾在中央政府、地方政府或者军队任职来衡量政治关系;分别用公司是否存在金字塔结构、公司层级以及两权分离程度来衡量股权结构。回归结果显示,EXIST-COMP和PROFIT-COMP系数仍显著为负,而HHI-COMP(PROFIT-COMP)系数在投资不足(投资过度)组仍为负但不显著。总体来看,控制公司政治关系和股权结构特征后,本文假说2仍然成立。
8参照Karuna(2007)的定义:产品的差异化,等于某一年度某一行业内所有上市公司营业收入总和除以营业成本总和;市场规模,等于某一年度某一行业内所有上市公司销售收入之和的自然对数;进入成本,等于某一年度某一行业内所有上市公司加权平均“固定资产、无形资产等净额”的自然对数,其中权重为各上市公司的市场占有率。与前文一致,我们在行业层面对三个指标进行了标准化处理。
9 Sargan检验结果显示,检验统计量(Score Chi2)在10%的置信水平上不能拒绝“所有工具变量均为外生”的原假设;在2SLS估计中第一阶段回归方程中工具变量的partial-R2均大于0.35,且对应的partialF值均大于100,表明工具变量与内生变量具有很高的相关性。满足工具变量有效性的两个条件。Hausman检验显示,借鉴Li(2010)方法衡量行业竞争程度时Wu-Hausman F统计量为1.858,在10%的置信水平上拒绝“原模型所有解释变量均为外生”的原假设,因而采用2SLS是必要的;而采用HHI指数衡量行业竞争时Wu-Hausman F统计量为0.907(P值为0.404),统计上不显著,意味着此处采用OLS也是有效的。
10 这里与Biddle et al.(2009)和Chen et al.(2011)的原始模型稍微不同的是,他们进行分年度分行业回归估计,而本文选择将行业特征作为哑变量在模型中加以控制并分年度回归。主要是由于本文重点考察的是行业层面的竞争因素对行业间投资效率差异的影响,如果采用分年度分行业回归,将消除行业间投资效率的差异,导致本文假说无法得到有效的检验。
11非常感谢匿名审稿人的建议,本文进一步从行业-年度层面重新检验研究假说。具体:第一,我们将公司-年度数据合成为行业-年度数据,共得到234个行业年度观测值;第二,采用Richardson(2006)模型以这些行业-年度观测值为样本进行回归并估计得残差;第三,参照Biddle et al.(2009)方法将行业-年度残差区分为投资不足和投资过度;第四,在行业-年度层面上进行投资效率的回归分析。回归结果显示,除了在投资过度组PROFIT-COMP的回归系数变得不再显著外,其余结论不受影响。