Market Competition and Selection
for the New Palgrave Dictionary of Economics,2nd ed.
Lawrence Blume??and David Easley?
June2007
Realized pro?ts,not maximum pro?ts,are the mark of success
and viability.It does not matter through what process of rea-
soning or motivation such success was achieved.The fact of its
accomplishment is su?cient.This is the criterion by which the
economic system selects survivors:those who realize positive prof-
its are the survivors;those who su?er losses disappear.
Alchian(1950)
1Introduction
Most economic models make use of extreme rationality hypotheses:?rms maximize pro?ts with full knowledge of their technology and prices,and, investors are subjective expected utility maximizers whose beliefs are correct. Surely,some?rms and some investors do not always behave as these models hypothesize.But does this matter for predictions of market outcomes?It could be that the aggregation that takes place in supply and demand results
2 in prices and market quantites that agree with the predictions of models using extreme verions of rationality.It could be that over time,?rms and investors learn to behave as these models predict and so over time market outcomes converge to those predicted by the models.Finally,it could be that markets select for?rms and investors who behave’as if’they are rational. This last defense of the use of rationality is the essence of the quote from Alchian(1950).
There is a long history in economics of using market selection argu-ments in defense of rationality hypotheses.The early literature focused on selection for pro?t maximizing?rms.Among its best known proponents is Friedman(1953):‘The process of natural selection thus helps to validate the hypothesis(of pro?t maximization)or,rather,given natural selection, acceptance of the hypothesis can be based largely on the judgment that it summarizes appropriately the conditions for survival.’Of course,even if the selection reasoning is correct,selection can only work over those types of behaviors which are present in the economy.If no?rm maximizes pro?ts, then no pro?t maximizing?rm can be selected.Alchian(1950)was acutely aware of this:‘The pertinent requirement—positive pro?ts through relative e?ciency—is weaker than‘maximized pro?ts,’with which,unfortunately, it has been confused.Positive pro?ts accrue to those who are better than their actual competitors,even if the participants are ignorant,intelligent, skilful,etc.The crucial element is one’s aggregate position relative to actual competitors,not some hypothetically perfect competitors.As in a race,the award goes to the relatively fastest,even if all the competitors loaf.’Enke (1951)argued that,at least in competitive industries,the relatively fastest will in fact be pro?t maximizers,and so,in this case selection will lead to the survival only of pro?t maximizing?rms:‘In the long run,however,if?rms are in active competition with one another rather than constituting a number of isolated monopolies,natural selection will tend to permit the survival of only those?rms that either through good luck or great skill have managed, almost or completely,to optimize their position and earn the normal pro?ts necessary for survival.In these instances the economist can make aggregate predictions as if each and every?rm knew how to secure maximum long-run pro?ts.’
Similar market selection arguments have been proposed to justify strong rationality hypotheses on the part of investors.Fama(1965)argues
3 that:‘...dependency in the noise generating process would tend to produce ‘bubbles’in the price series...If there are many sophisticated traders in the market,however,they will be able to recognize situations where the price of a common stock is beginning to run up above its intrinsic value.If there are enough of these sophisticated traders,they may tend to prevent these ‘bubbles’from ever occurring.’According to Fama,‘A superior analyst is one whose gains over many periods of time are consistently greater than those of the market.’This is at least indirectly an argument for market selection and its a?ect on the e?ciency of prices.Cootner(1964)was an early,clear proponent of this argument:’Given the uncertainty of the real world,the many actual and virtual traders will have many,perhaps equally many,forecasts...If any group of traders was consistently better than aver-age in forecasting stock prices,they would accumulate wealth and give their forecasts greater and greater weight.In this process,they would bring the present price closer to the true value.’
In this entry we examine the more recent work which has analzyed whether these arguments for market selection,and its impact on e?ciency, are correct.We consider in turn,selection over?rms,and,selection over investors.
2Selection over Firms
The argument made by Alchain,Friedman,and Enke is that a pro?t dynamic will select for?rms that for whatever reason maximize pro?ts.Correspond-ingly,according to this argument,those who do not act as pro?t maximizers will be driven out of the market.But how is it that non-maximizers are driven out?The implicit idea is that in the presence of maximizers,the non-maximizers experience losses which deplete their?nancial capital,and this forces them out of the market.The literature has explored two avenues by which losses of?nancial capital could have this e?ect.One is that if the ?rm’s operations are?nanced from retained earnings,then?rms which con-sistently experience losses would eventually exhaust their retained earnings causing them to vanish.A second argument is that unsuccessful?rms will not be able to raise capital in the?nancial markets,and may not even be
4 able to retain their initial capital.Thus,so this story goes,the markets will punish unsuccessful?rms and they will eventually vanish.
Winter(1964,1971)and Nelson and Winter(1982)analyze a retained earnings dynamic.They argue that the retained earnings of pro?t maximizers will grow fastest,and thus these?rms will eventually dominate the market. Nelson and Winter construct a partial equilibrium model in which the“as if”hypothesis of pro?t maximization describes the long run steady state behavior of?rms.In their analysis,prices are?xed and all?rms have access to the same technology.This structure leads to the existence of a uniformly most?t?rm which is selected for by a retained earnings based investment dynamic.
The early work on market selection was greatly concerned with the meaning of pro?t maximization when pro?ts are random.Dutta and Rad-ner(1999)directly take up the question of whether markets select for?rms that maximize expected pro?ts.Their answer is no:the decision rules which maximize the long probability of survival are not those that maximize ex-pected pro?ts.Dutta and Radner’s?rms are owned by investors who choose how much of the?rm’s earnings to reinvest in the?rms and how much to withdraw as dividends.An expected pro?t maximizing?rm is one which maximizes the expectation of present discounted value of dividends paid to its owners.This policy results in an upperbound on the retained earnings left in the?rm and from this level of retained earnings any?rm can experience a string of losses that result in bankrupcy.
There are two parts to the argument for market selection of pro?t maximizers.First,there is the issue of whether the market selects for pro?t maximizers.Second,there is the issue of whether in the long run the econ-omy behaves as if only pro?t mazimizing?rms exist.The Dutta and Radner analysis raises doubts about a positive answer to the?rst question in stochas-tic settings.Koopmans(1957)raised doubts about a positive answer to the second question even in a determnistic setting.According to Koopmans, appealing to an external dynamic process to defend the pro?t maximization assumption is not a satisfactory way to proceed.Instead,he believed that the dynamic process itself should be modeled.Nelson and Winter(1982,p.158) were also aware that the coevolution of?rm behavior and the economic envi-ronment resulting from a complete model of the dynamic process could pose
5 problems for the evolutionary defense of pro?t maximization.They observed that among the“...less obvious snags for evolutionary arguments that aim to provide a prop for orthodoxy...”is“...that the relative pro?tability ranking of decision rules may not be invariant with respect to market condi-tions.”They do not,however,go on to provide a general equilibrium analysis of the consequences of replacing static pro?t maximization with a selection dynamic.
Blume and Easley(2002)showed that Koopman’s concern about the market selection dynamic in a general equilibrium setting is correct.They show that although only pro?t maximizers persist in any steady state of the retained earnings dynamic,the long run of the economy need not be well described by assuming that only pro?t maximizing?rms exist.The di?culty arises because of the endogeniety of prices which causes the relative pro?tability of?rms to depend on the allocation of capital across the?rms. As a result,the retained earnings dynamic need not settle down,and e?cient ?rms can be driven out of the market by ine?cient?rms.
In addition to raising working capital through retained earnings,?rms also enter the capital markets.Whether these markets reinforce the market selection hypothesis,as Friedman argues,or undermine it,depends on how well these markets function.If markets are complete(without the securities created by non-maximizing?rms)and investors are expected utility maxi-mizers with rational expectations,then investors would not allocate capital to non-maximizing?rms.Such?rms would never produce,and the the se-lection hypothesis would be trivially,and instantly,correct.Alternatively,if some investors have incorrect expectations,then they could invest in non-maximizing?rms.The fate of these?rms depends on the fate of their in-vestors.So in this case,the question of selection for pro?t maximizing?rms reduces to the question of selection for investors who act as expected utility maximizers with rational expectations.
3Selection over Investors
Friedman,Fama and Cootner argue that asset markets will select for rational investors,and that because of this selection,assets will eventually be priced
6 e?ciently.Two interesting approaches have been taken to the selection for rational investors question.First,suppose traders use a variety of portfolio rules.Is it the case that traders whose rules are not rational rules will lose their money to those who do act as if they are rational?Second,suppose that all traders are subjective expected utility maximizers.Is it the case that markets select for those whose expectations are correct,or most nearly correct?
In order to pose these questions precisely rationality has to be de?ned (see rationality).The selection literature has asked about selection for a very strong form of rationality—expected utility maximization with correct expectations about the payo?s to assets.This is the interesting question because in economies populated by subjective expected utility maximizers whose beliefs are not tied down by a rational expectations hypothesis we have little to say about asset prices.Assuming only that investors are sub-jective expected utility maximizers(in the sense of Savage(1951))places no restrictions on the stochastic process of Arrow security prices(Blume and Easley2005).
3.1Selection over Rules
Consider an intertemporal general equilibrium economy with a collection of Arrow securites and one physical good available at each date.Suppose traders are characterized by their stochastic processes of endowments of the good and by portfolio and savings rules.A savings rule describes the fraction of his wealth the trader saves and invests at each date given any partial history of states.Similary,a portfolio rule describes the fraction of his savings the trader allocates to each Arrow security.The savings and portfolio rules that rational traders could choose form one such class of rules.But other, non-rationally-motivated rules are also possible.
There are two questions to ask about the dynamics of wealth selection in this economy.First,is there any kind of selection at all?Is it possible to characterize the rules which win?Second,if selection does take place, does every trader using a rational rule survive,and in the presence of such a trader do all non-rational traders vanish?
7 In repeated betting,with exogeneous odds,the betting rule which maximizes the expected growth rate of wealth is known as the Kelly Rule (Kelly1956).The use of this formula in betting with?xed,but favorable odds was further explored by Breiman(1961).In asset markets the“odds”are not?xed,instead they are determined by equilibrioum asset prices,which in turn depend on traders’portfolio and savings rules.Nonetheless,the market selects over rules according to the expected growth rate of wealth share they induce.Blume and Easley(1992)show that if there is a unique trader using a rule which is globally maximal with respect to this criterion,then this trader eventually controls all the wealth in the economy,and prices are set as if he is the only trader in the economy.A trader whose savings rate is maximal and whose portfolio rule is,in each partial history,the conditional probability of states for tomorrow has a maximal expected growth rate of wealth share.This rule is consistent with the trader having logarithmic utility for consumption,rational expectations and a discount factor that is as large as any trader’s savings rate.Thus,if this trader exists,he is selected for. However,rationality alone does not guarantee a maximal expected growth rate of wealth share.There are rational portfolio rules that do not maximize ?tness(even controlling for savings rates)and traders who use these rules can be driven out of the market by traders who use rules that are inconsistent with rationality.
Amir,Evstigneev,Hens,and Schenk-Hoppe(2005)and Evstigneev, Hens,and Schenk-Hoppe(2006)take an alternative approach to selection over rules in asset markets.They consider general one-period assets and ask if there are simple portfolio rules that are selected for,or are evolutionarliy stable,when the market is populated by other simple(not explicitly price dependent)portfolio rules.In this research,either all winnings are invested, or equivalently investors are asssumed to invest an equal fraction of their winnings.So selection operates only over portfolio rules.Amir,Evstigneev, Hens,and Schenk-Hoppe(2005)?nd that an investor who apportions his wealth across assets according to their conditional expected relative payo?s drives out all other investors as long as none of the other investors end up holding the market.This result is consistent with Blume and Easley(1992) as the log optimal portfolio rule agrees with the conditional expected relative payo?rule when only these two rules exist in the market.Hence,both of these rules end holding the market in the limit.Evstigneev,Hens,and Schenk-Hoppe(2006)show that the expected relative payo?s rule is evolutionarily
8 stable using notions of stability from evolutionary game theory.
3.2Selection among Subjective Expected Utility Max-
imizers
DeLong,Shleifer,Summers,and Waldmann(1990)and DeLong,Shleifer, Summers,and Waldmann(1991)analyze selection over traders who are sub-jective expected utility maximizers with di?ering beliefs.DeLong,Shleifer, Summers,and Waldmann(1990)shows,in an overlapping generations model, that traders with incorrect beliefs can earn higher expected returns.They do so because they take on extra risk.But as survival is not determined by expected returns,this result does not answer the selection question.DeLong, Shleifer,Summers,and Waldmann(1991)argues that traders whose beliefs re?ect irrational overcon?dence can eventually dominate an asset market in which prices are set exogenously.This result appears to contradict Alchian’s and Friedman’s intuition.But,as prices are exogeneous,these traders are not really trading with each other;if they were,then were traders with in-correct beliefs to dominate the market,prices would re?ect their beliefs and rational traders might be able to take advantage of them.
In an economy with complete markets,and traders who have a com-mon discount factor,Alchain and Friedmans’s intuition is correct.Sandroni (2000)shows,in a Lucas trees economy,with some rational-expectations traders that,controlling for discount factors,all traders who survive have ra-tional expectations.Blume and Easley(2006)show that this result holds in any Pareto optimal allocation in any bounded classical economy,and thus for any complete markets equilibrium.To see why the market selection hypoth-esis is true for these economies suppose that states are iid and that traders have di?ering,?xed iid beliefs.Then each trader assigns zero probability to almost all the in?nite sample paths that any other trader believes to be possible.Each trader would be willing to give up all of his endowment on the sample paths he believes to be impossible in order to obtain more consump-tion on those he believes to be possible.Since markets are complete,these trades are e?ectively possible.But,if only one trader has correct beliefs, then only one trader puts positive probability on the in?nite sample paths that actually occur.So only this trader will have positive consumption,and
9 thus positive wealth,in the limit.
For bounded complete markets economies there is a survival index that determines which traders survive and which traders vanish.This index depends only on discount factors,the actual stochastic process of states and traders beliefs about this stochastic process.Most importantly,for these economies,attitudes toward risk do not matter for survival.The literature also provides various results demonstrating how the market selects among learning rules.The market selects for traders who learn the true process over those who do not learn the truth,for Bayesians with the truth in the support of their prior over comparable non-Bayesians,and among Bayesians according to the dimension of the support of their prior(assuming that the truth is in the support).
In economies with incomplete markets,the market selection hypoth-esis can fail to be true.Blume and Easley(2006)shows that if markets are incomplete,then rational traders may choose either savings rates or portfolio rules that are dominated by those selected by traders with incorrect beliefs. If some traders are irrationally optimistic about the payo?to assets,then the price of those assets may be high enough so that rational traders choose to consume more now,and less in the future.Their low savings rates are optimal,but as a result of their low savings rates the rational traders do not survive.
An alternative version of the market selection hypothesis is that as-set markets select for traders with superior information.The research dis-cussed above asks about selection over traders with di?erent,but exoge-neously given,beliefs.Alternatively,if traders begin with a comon prior and receive di?erential information they will have di?ering beliefs,but now they will care about each others beliefs.In this case,the selection question is di?cult because the information that traders have will be re?ected in prices. If the economy is in a fully revealing rational expectations equilibrium,then there is no advantage to having superior information,see Grossman and Stiglitz(1980).So the question only makes sense in the more natural,but far more complex,case in which information is not fully revealed by market statistics.Figlewski(1978)shows that traders with information which is not correctly re?ected in prices have an advantage in terms of expected wealth gain over those whose information is fully impounded in prices.But as ex-
10 pected wealth gain does not determine?tness this result does not fully answer the question.Mailath and Sandroni(2003)consider a Lucas trees economy with log utility traders and noise traders.They show that the quality of information a?ects survival,but so does the level of noise in the economy. Scuibba(2005)considers a Grossman and Stiglitz(1980)economy in which informed traders pay for information and shows that in this case uninformed traders do not vanish.
4Conclusion
The modern literature has shown that the market selecion hypothesis needs to be quali?ed.For some economies it acts much as the earlier writers conjec-tured;in others it does not select for pro?t maximizers or rational traders. Much work remains to be done,however.Blume and Easley(1992)and Sandroni(2000)mostly discuss selection in complete markets.Sandroni, however,points out that even when markets are incomplete,traders with log utility and rational expectations are favored,while Blume and Easley construct some examples to show that the outcome of market selection can depend on market completeness.The connection between market structure and market selection is not well-understood.The implications of market se-lection for asset pricing are known only for complete markets in the long run and some examples.Most economists’intuition about market behavior and asset pricing comes from the study of market models which allow little or no agent heterogeneity.Taking heterogeneity seriously and chasing down its implications for market performance promises to be a rich area for future research.
11 References
Alchian,A.(1950):“Uncertainty,Evolution and Economic Theory,”Jour-nal of Political Economy,58,211–221.
Amir,R.,I.Evstigneev,T.Hens,and K.R.Schenk-Hoppe(2005):“Market Selection and Survival of Investment Strategies,”Journal of Mathematical Economics,41,105–122.
Blume,L.,and D.Easley(1992):“Evolution and Market Behavior,”Journal of Economic Theory,58(1),9–40.
(2005):“Rationality and Selection in Asset Markets,”in The Econ-omy as an Evolving Complex System,ed.by L.Blume,and S.Durfaul, p.xx.Oxford University Press,Oxford.
(1991):“The Survival of Noise Traders in Financial Markets,”Journal of Business,64(1),1–19.
Dutta,P.,and R.Radner(1999):“Pro?t maximization and the market selection hypothesis,”Review of Economic Studies,66(4),769–798. Enke,S.(1951):“On Maximizing Pro?ts:A Distinction Between Cham-berlin and Robinson,”American Economic Review,41(4),566–578.
12 Evstigneev,I.,T.Hens,and K.R.Schenk-Hoppe(2006):“Evolu-tionary Stable Stock Markets,”Economic Theory,27,449–468.
F ama,E.(1965):“The Behavior of Stock Market Prices,”Journal of Busi-ness,38(1),34–105.
Figlewski,S.(1978):“Market’E?ciency’in a Market with Heterogeneous Information,”Journal of Political Economy,86(4),581–597.
Friedman,M.(1953):Essays in Positive Economics.University of Chicago Press,Chicago.
Grossman,S.J.,and J.E.Stiglitz(1980):“On the Impossibility of In-formationally E?cient Markets,”American Economic Review,70(3),393–408.
Kelly,J.L.(1956):“A New Interpretation of Information Rate,”Bell System Technical Journal,35,917–926.
Koopmans,T.(1957):Three Essays on the State of Economic Science. McGraw-Hill Book Co.,New York,NY.
Mailath,G.,and A.Sandroni(2003):“Market Selection and Asymmet-ric Information,”Review of Economic Studies,70,343–368.
Nelson,R.,and S.Winter(1982):An Evolutionary Theory of Economic Change.Harvard University Press,Cambridge,MA.
Sandroni,A.(2000):“Do Markets Favor Agents Able to Make Accurate Predictions?,”Econometrica,68(6),1303–42.
Savage,L.J.(1951):“The theory of statistical decision,”Journal of the American Statistical Association,46,55–67.
Scuibba,E.(2005):“Asymmetric Information and Survival in Financial Markets,”Economic theory,25(2),353–379.
Winter,S.(1964):“Economic Natural Selection and the Theory of the Firm,”Yale Economic Essays,4,225–272.
关于商务英语的情景对话 对代理请求的回应 401. As the volume of business concluded by you is not big enough, we won t consider the question of agency. 鉴于贵方去年成交的数额不大我方不会考虑代理的问题。 402. We think it premature for us to discuss the question of agency at present stage. 我方认为现阶段讨论代理的问题对我方来说还为时过早。 403. The time is not yet mature to discussion of agency. 讨论代理的时间还不成熟。 404. We would like to say that this initial stage contract between us, both side do not understand each other very well, so there seems to be no sufficient bases for us to negotiate agency. 我方想要说的是在我们履行合同的初期双方的相互了解还不够因此我们讨论代理的条件还不太具备。 405. I am afraid that this is not good time yet to push the sales of our product in your market. 恐怕现在还不是在贵方市场上推销我方产品的时机。
406. We do not think the time is right for the discussion of the question of e_clusive agency. 我们认为讨论独家代理问题的时机尚不成熟。 407. We regret to say that since there is so far no transaction concluded between us, we have to decline your quest for agency. 由于我们双方迄今未成达任何交易很遗憾我方不得不拒绝贵方申请代理的要求。 408. The question of agency is still under consideration and we hope you will continue your effort to push the sale of our product at present stage. 代理的问题还在考虑中我方希望在现阶段贵方还要继续努力推销我方的产品。 409. We shall not consider pointing you as our sole agent until your sales record justify our doing so. 待你们的销售成绩足以表明可以委托你方独家代理时我们才会考虑此事。 410. Shall we discuss the matter of agency when your market condition turns better 我们是否等到中方市场情况好转时再来谈代理的事情好吗 代理条件和要求
商务英语期末考试参考答案 说明：商务英语期末考试有五种题型： 一、中英短语互译已经全部总结，见下文 二、问答题已经提供了参考答案，仅供参考，见下文 三、案例分析题请根据题目要求自行准备 四、英语段落翻译中文已经注明，请自己翻看商务英语教程 五、写作请根据题目要求自行准备 1、中英短语互译（详见商务英语课件——每个PPT中的短语部分） PPT1： 1. individual proprietorship个体经营，独资企业 2. convertible bonds 可转换债券 3. memorandum of association 公司章程 4. monopolistic competition 垄断竞争 5. business credit 商业信用 1. 财政资源 financial resources 2. 有限责任公司 limited company 3. 销售收入 sales revenue 4. 有形商品 tangible goods 5. 流动资金 working capital PPT2： 1. flexible manufacturing system 弹性生产系统 2. fractional reserve system 部分准备金制度
3. credit instruments 信用工具，信用票据 4. bull market/bear market 牛/熊或多头/空头市场 5. manufacturing process 制造工艺 1. 厂址选择 facility location 2. 库存控制 inventory control 3. 总支出 aggregate expenditures 4. 股权证/权益证 equity instruments 5. 财务管理 financial management PPT3： 1. performance appraisal 绩效/业绩评估 2. promotion-from-within 内部提拔 3. skills inventory 技术库存 4. macroeconomic ramification 宏观经济衍生物/结果 5. closed-end fund 封闭式基金 1. 项目生命周期 project life cycle 2. 软技能和硬技能 soft skills and hard skills 3. 补偿制度 compensation system 4. 开放式基金 open-ended fund 5. 优先股 preferred stock PP4： 1. profit-oriented objective 利润导向的目标 2. marketing intermediary 营销代理商
经典大学毕业演讲致辞经典大学毕业演讲稿毕业季又如期而来，大学毕业生如何做好演讲致辞呢?以下是由关于经典大学毕业演讲致辞的内容，希望大家喜欢! 尊敬的领导、来宾，亲爱的老师、同学们： 大家好! 我是厦门大学人文学院哲学系XX届博士毕业生，曾永志。非常荣幸能够作为XX届毕业生代表在此发言，请允许我代表人文与艺术学部的全体毕业生向亲爱的母校致以崇高的敬意，向辛勤培育我们的老师以及家长表示由衷的感谢! 身为厦大人，我们是幸福的。本科四年，硕博五年，我在厦大度过了最美好的时光。最美丽的校园、最具魅力的老师们、最可爱的同学们，定格为此刻的记忆，一笔一划镌刻在心中，成为永恒的纪念与财富。凌晨，南普陀寺的钟声还声声在耳;清早，芙蓉湖畔结伴读书的画面还历历在目;夕阳西下，上弦场上，挥汗踢球、轻松漫步、依山看海的种种也犹在昨日。美丽的母校依然美丽，而我们，在各自的三年、四年、七年、九年，亦或十年里，悄然成长。 身为厦大人，我们是富足的。从九年前的集美中学到现在的厦门大学，陈嘉庚先生的精神，始终照耀着我的求学生涯。九年里，每当我漫步校园，身边的一砖一瓦无不镌刻着创校先贤们的痕迹：嘉庚先生的民族大义，倾资办学;罗扬才烈士的革命精神，奋不顾身;萨本栋校长的迁学闽西，自强不息;王亚南校长、陈景润教授的刻苦钻研，科学至上，无不让我身怀感慨。
九年里我见证了母校的点滴变化：从“421”住宿环境到米饭，我们的学习没有了后顾之忧;从湖畔咖啡到校长早餐有约活动，我们更广泛地参与学校事务的决策;从优博培育工程到国际交换生项目，我们以更积极的姿态迈向世界。有此历史，有此文化，有此校园，我们厦大人青春与幸福同行。 身为厦大人，我们是广博的。我们的厦大是一所校门向大海敞开的大学。她用海纳百川的胸襟包容、尊重每个学生，让每个独立的存在都具有无可取代的价值;她用春暖花开的气度培育、锻造每位青年，让每个人都拥有自己独立的空间、绝对的人格;她用感恩、责任、奉献的情怀熏陶、感染每名学子，让每一个充满个性的灵魂同时具备深深的社会责任感，肩负起时代使命。宽容与大爱，是我们厦大的品格，更是我们厦大人永远的精神品质。 身为厦大人，我们是幸运的。我们专业的老师们，以他们严谨的治学态度、前沿创新的学术思想、开拓进取的科研精神，引领我们在科学研究的道路上大步向前。仍记得，在博士论文完成之际，正值厦大90周年校庆，我的导师百忙之中仍为我三易初稿，细致到甚至是对“方面”与“部分”这两个概念的区分。那本先生在旅途的车上用铅笔注得密密麻麻的论文，已成为我毕生的珍藏。我们的政工、行政及后勤等老师们，他们与我们相互理解，相互尊重，分享彼此的经历与思考，指引我们获得更积极健康的思想情怀与人生经验。 或许，我们无以回报，唯有谨记。但我相信，在座的每一位毕业生同学都将与我一样，带着母校的关爱，带着厦大人自强不息的精
设计、开发和评估低成本的温室技术以适应寒冷的沙漠条件 INDU BHUSHAN BHAGAr’, It R. KIJMAR AND ASHWANI KUMAR’ ‘College of Agricultural Engineering, Dapariment of Irrigation & Drainage Engineering, Rajendra Agriculwral University. Bihar Peso (Samastipur) 848125. India :tvyua Bhubaneshwar (Otissa), India Correspondence 气候参数的研究和应用的温室技术创业作物生产在寒冷的沙漠地区的Spiti山谷地区做了。这项研究表明,江青在寒冷的环境条件的莫迪沙漠地区温室技术couldgrow蔬菜作物适应。不同形状的绿色房子结构构造和灵活性的蔬菜作物越来越像甜菜叶子、香菜、生菜、番茄、茄子、薄荷、mcdii、卷心菜、黄瓜进行了研究。海沟类型温室提供优于收益率泰坦其他类型的温室结构和生产的甜菜叶子蔬菜ws发现所有蔬菜中最高。得出温室技术是一个成功的技术存在的问题和寒冷的沙漠地区,人们可以在更大程度上减少 关键词气候、温室、垃圾生产。成本,沙漠的条件。 阱热辐射(长期波动)物体发出的在(2)。在温度和fls的二氧化碳水平在绿色房子负责蔬菜和其它作物的生产力量在寒冷的climateconditions。低成本温室是一个简单的结构,采用本地可用的材料,如竹子和蒂姆误码率(3)。UV-stabilised聚乙烯薄膜作为穿衣-?丁材料。与传统的温室,没有具体的控制设备调节环境因素在温室提供。然而简单的技术采用操纵燕鸥ptrature和相对湿度。使用材质交配——als和网络可以减少甚至光的强度。Thetem高温可以redupced duering wnarm obe seiasonbyg所有侧墙。这样的结构也被用作避雨提高作物。否则内部温度温室里的增加在边墙上的吗fihn覆盖着塑料。印度的寒冷沙漠区位于高海拔范围西北部的喜马拉雅山脉的最北部的拉达克地区县覆盖ofiammu贡献度和克什米尔和Lahul-Spiti di-视觉ofHimachal邦。这个地区是rized成立由高海拔(2700 - 4600),桑迪moun tains,非常低的温度(-40 C),16 w相对湿度(40%到),低氧浓度在空气和低降水(80 - 300毫米),主要在雪的形式,时间短(120 - 150天)的种植季节(5月到9月)。欧元区的展品更大的多样性的土壤、地形和cli交配的寒冬,高风和低降雨。印度有大约74809的kin2寒冷的沙漠地区查谟和克什米尔的状态和喜马偕尔邦。查谟和克什米尔代表总数的87.4% regiovn coldoarid whereaseHimacharl邦12.60%(4)。在小口袋ofGharhwalSimilarclimaticeonditionsarealsomet Badrinath之外(镍钛和法力)和Nelang地区的Uttarkashi Uttaranchal(5)。寒冷干旱环境harshing,andunpredictabie不稳定。这是不可能在田间种植任何作物在这些区域大胆冬天。因此,self-sustenance不仅是期望水机还强制性的地区方面发展。温室技术意味着生产的植物使用覆盖的经济结构,它允许快速收集太阳辐射和修改agro-dlimate条件有利于植物的生长和发展。这项技术包含infra结构、建模和adoptation作物的选择、生产经济学、农艺男人管理和商业潜力。低成本的绿色房屋技术可以提升经济增长的几种方法更喜欢的蔬菜生产和绿色的蔬菜,在冬季(6),温室成形工艺中的技术是一个可行的选择对这些问题。通过采用温室技术、气候param片式可以修改和条件可以作出有利于一些作物生产活动。一个在吸引了研究响应ofcrop增长!收益率在寒冷的沙漠条件下温室。天气寒冷的沙漠的特殊性i.e.high tem高温波动;强风和高紫外线辐射光的强度,再加上不同的需求类型 的ent温室的地区。通常该地区被孤立于主要的土地和保持土地锁住大部分的几个月在此后一年所有需要的材料为温室必须本地可用的和成本低廉,这样可怜的部落农民可以负担得起费用。他有足够的能力的温室必须捕获太阳能和生产蔬菜甚至在零下的温度(7),也应该足以抵挡强烈的寒潮和极低的温度下。结构应该简单和容易managethle,所以即使是一层-人可以建立和管理它没有任何困难。保持这些记点不同类型的绿 色房屋被构造和性能的评估通过种植蔬菜creps在德签署了结构。
目录 Day today Office日常事务 1 Faxes传真 2 Telephone Calls电话 3 Making Telephone Appointments电话预约 4 Memos备忘录 5 Business Correspondence商业信函 6 Placing an Order下订单 Office Talk办公室谈话 7 Coworkers同事 8 Bosses老板 9 Brainstorming集体讨论 10 Commuting乘公交车上下班 11 The Working Lunch工作午餐 Business Trip商务旅行 12 International Business Travel国际商务旅行 13 Dressing for Business商务着装 14 Hotel Situations旅馆情景 15 Negotiating the Subway乘地铁 Client Reception接待客户 16 Receiving Clients接待客户 17 Entertaining Clients招待客户 18 Accommodating Foreign Clients接待国外客户 19 Factory Tours参观工厂 Business Communization商务交流 20 Personal Introductions个人介绍 21 Small Talks聊天 22 Delivering Bad News传达坏消息 23 Polite Questions礼貌提问 24 Farewells道别 Negotiation谈判 25 Clarifying the Stakes说明利害关系 26 Making Concessions做出让步 27 Discussing the Bottom Line讨论底线 28 Accepting and Confirming接受和确认29 Hard Bargainers VS Soft Bargainers强硬的对手和温和的对手 Company Organization公司结构 30 CEO执行总裁 31 Stockholders股东 32 Board of Directors董事会 33 Managerial Staff管理人员 34 Labor Staff普通员工 Meetings and Interviews会议和面谈 35 Executing Meetings开会 36 Performance Reviews业绩评估 37 Agendas会议议程 38 Making Requests提出要求 Presentations业务陈述 39 Preparation and Developing Your Topic准备和展话题 40 Introductions and Beginnings介绍和开头 41 Making Transitions in the Present ation陈述中的过渡 42 Conclusions结论 提问阶段Data数据处理 44 Trends趋势 45 Systems制度 46 Scheduling日程安排 47 SWOT An山sis态势分析 48 Statistical Reports数据统计报告 Technology技术 49 Ema il电子邮件 50 Computer Technology计算机技术 51 Running an Inte rn et Business网上做生意 52 Electronic Gadgets数码产品 53 Web based Marketing网上营销 Financial Topics财务话题 54 Costing成本
国开04009商务英语1任务6参考答案 说明：如果课程题目是随机的，请按CTRL+F在题库中逐一搜索每一道题的答案 题目1：— What if he still doesn't pay up? — : If it's a small amount we write it off as bad debt. For larger sums we… ; I've got to hurry. ; I have already done that. 标准答案：If it's a small amount we write it off as bad debt. For larger sums we… 题目2：—The senior managers need the results from last month straight away, so I can’t stop to talk. I’ve got to hurry. — : Go slowly. ; Stay longer. ; Ok, see you later. 标准答案：Ok, see you later. 题目3：—Hello, Sally. What’s the matter with you? You look worried. — : What shall I do if a customer doesn’t pay up on the due date? ; Yeah, that’s true. It requires great attention. ; Don’t mention it. 标准答案：What shall I do if a customer doesn’t pay up on the due date? 题目4：He didn’t seem to any actions. : make ; do ; take 标准答案：take 题目5： your check is received within a week we shall have no alternative. : Unless ; As ; If 标准答案：Unless 题目6：二、阅读理解：阅读下面的对话，选择合适的内容将对话补充完整。
大学毕业典礼发言稿 大学只有短短的四年的时间，终究会随着时光的步伐走到毕业的那 一天。 曾经是多么的盼望着早些离开校园、离开宿舍、离开课堂、离开书本、离开学生的称呼，但到了真正不得不离开的那一刹那，才知道，自 己对这片土地是多么的留念。在这里，留下了我最最美好的回忆和记 忆。 几年的课堂，老师们或滔滔不绝，或循循善诱，或旁征博引的风格，为我们展现了知识的无限魅力。如果黑板就是浩淼的大海，那么，老师 便是海上的水手。铃声响起那刻，你用教职工鞭作浆，划动那船只般泊 在港口的课本。课桌上，那难题堆放，犹如暗礁一样布列，你手势生动 如一只飞翔的鸟，在讲台上挥一条优美弧线——船只穿过……天空飘不 来一片云，犹如你亮堂堂的心，一派高远。 许还有一些遗憾吧，那么多精彩的讲座，我们已经来不及聆听;那 么多精彩的活动，我们已经来不及参与。也许还有一些愧疚吧，面对慈 父严母般的老师，我们总能杜撰出各种逃课的理由。面对认真批改作业 的各科老师，我们很多时候都只能拿出一个版本。 大学毕业典礼发言稿 怀着梦想和激情走进大学的校门，开始一段新的人生旅程。转眼离 别的时候就要到了，真希望时间慢些走，让我再多点时间好好享受下大 学里的生活，友谊。大学的生活真好，回忆起来诸多辛酸苦辣。
那是因为您，亲爱的母校。是您包容了我们的懂无知，是您孕育 了我们的睿智果断，是您给了我们如此优越的学习环境和展示自我的舞台。我们在教室留下刻苦学习的身影，在球场上留下顽强拼搏的精神， 在舞台上秀出个性自我，在通宵晚会里变换角色体味人生。我们沉浸在 知识的海洋，徜徉在落英缤纷的林荫道，醉心于同学间的欢声笑语。在 您的怀抱中，我们心怀梦想，放飞梦想。 最近，我常常考虑一个问题：假如我可以再度过一次大学生活，又 会选择怎样的生活方式?会努力地追求些什么?放弃些什么?有些问题真 的会有和当时不一样的答案。 首先我想谈谈我在大学的收获。其实原先没有想到这个问题，上回 应聘主考官问我这，记得当时为了求职说了些冠冕堂皇的话，现在觉得 大学我的收获并不是学到了多少知识，也并不是受到了那个教授，老师 的熏陶，点拨，而是学会了怎么去为人处世，怎么去独立，怎么去快乐 的生活，怎么去正确的看待，分析社会的一些问题。这也许就是所谓的 成熟吧，我觉得这些应该比知识还要重要些。 在中学同学印象中我也许是个勤奋，刻苦努力的人，但是在大学同 学印象中，他们原话是你活的比较悠闲，其实意思是懒散，呵呵。确实，大学我包过夜，挂过科，顶撞过老师，逃课，抄作业是很正常的事，但 是我并不认为这就是所谓的堕落，一方面因为我觉得初中是身体上累， 高中是精神上累，大学有时只是想让自己随心所欲的生活一下，但还是 有些人说看见你天天开开心心的，一定能长寿的，很高兴我大学里学会 了怎么去让自己快乐的生活，也带给身边的人快乐。另一方面我还是知
The Impact of Mother to Helen Each individual is extremely grateful to mother’s tending and educating. The influence of mother is anywhere but subtle. Sometimes we are unaware of the influence on our attitudes and behaviors. Helen Foster Snow was deeply influenced by her mother, without whom it could be extremely difficult to understand Helen with her attitude towards various challenges and her great motivation and desire for making success. In her struggle for kindness, Helen had had experiences such as being brave to be the first, acting as heroic and fearless and daring to take risks. All above came from her mother’s influence when Helen was young. Hannah Davis Foster, mother of Helen, devoted all her life to public service and her affairs. To improve lives of women and children, Hannah forged ahead and worked very hard. She was once a teacher, a businesswoman and even led community work. Energetic and creative, Hannah always participated in service activities in community with Helen around her, working selflessly for the development of society. Although she was a women leader, Helen’s mother always did men’s work. For example, she build house herself. Before Helen was 15, she stayed with her mother and learned from her mother during the whole process of her growth and development. In the period that Helen was to be an adult, she absorbed her mother’s crave for accomplishing gracious undertakings and the awareness of serving for the others. Helen’s mother worked very hard all her life and always worked over times. She built parks and playgrounds for children. Also she established the system of tutorship and she hoped that children could grow healthily, becoming physically- strong, noble-thinking, good-attitude and normative-behavior. As Helen’s mother put it, it was of great importance to adhere to good values and take pleasure in helping others, which she instructed Helen in a methodical and patient way. Helen emphasized on good morals which was a proof that her mother indeed influenced her. If we compared Ha nnah’s life with Helen’s experience, we will find many similarities. In 4th July, 1910, seated in the float for woman suffrage, Hannah took part in the
商务英语情景对话 A: seller B: buyer A: Hello, welcome to XX company, I’m the (职位). These are my Colleague , Miss … and Miss …. B: Hi, nice to meet you. I’m the (职位)，from XX company,(城市，国家) A: Nice to see you, too. Here is our catalogue for your reference. Is there anything particular you’re interested in? B: Well, I’m interested in your golden delicious apple. A: You have a good judgment. Golden delicious apple is famous as its first class quality, rich juice, and sweet sour taste. It’s also produced from Shandong province which has a good reputation of apples. B: well, I’m very impressed .May I have some idea of your price? A: Sure, USD 2000 per ton, CIF Newyork.(
B: Your price for golden delicious apple at USD 2000 per ton is on the high side, I can’t accept it. A: You must be aware that the price of golden delicious apple has been increasing since last year. It is fixed according to the upward trend in the international market price. B: But your price is much higher than the market price .Thailand gives a much lower price. A: The quality of this kind of golden delicious apple is much better. I can quote you on apple of quality and the price will definitely be lower. Our price varies according to the quality. B: What i mean is that your price is higher than of the same quality .It will be hard for us to persuade our clients to accept such a price .And as I known, many suppliers are in fact cutting the price trying to get a large market share. A: But our product can deal with the competition .You can see that we have already got many orders and more are coming. It shows that our product and price are acceptable
广东外语外贸大学成人高等教育 商务英语（专科）2018学年第1学期 《商务英语阅读》试题（A 卷） 年级： 考试形式：闭卷 考试时间：90分钟 Part I Multiple Choices (15 points, 1 point each) Direction : There are 15 incomplete sentences in this part. For each sentence there are four Choices 1. The fifth generation computers, with artificial intelligence, _______ and perfected now. A. developed B. have developed C. are being developed D. will have been developed 2. Y ou _______ her in her office last Friday; she’s been out of town for two weeks. A. needn’t have seen B. must have seen C. might have seen D. can’t have seen 3. She’s always been kind to me – I can’t just turn ______on her now that she needs my help. A. my back B. my head C. my eye D. shoulder 4. Careful surveys have indicated that as many as 50 percent of patients do not take drugs _______ directed. A. like B. so C. which D. as 5. The _______ goal of the book is to help bridge the gap between research and teaching, particularly the gap between researchers and teachers. A. joint B. intensive C. overall D. decisive 6. W e can accept your order _______ payment is made in advance. A. in the belief that B. in order that C. on the excuse that D. on condition that 7. The medical experts warned the authorities of the danger of diseases in the _______ of the earthquake. A. consequence B. aftermath C. results D. effect 8. Research universities have to keep up with the latest computer and scientific hardware _______ price. A. on account of B. regardless of C. in addition to D. not to mention 9. I am surprised _______ this city is a dull place to live in. A. that you would think B. by what you are thinking C. that you should think D. with what you were thinking 10. Don’t let the child play with scissors _______ he cuts himself. A. in case B. so that C. now that D. only if 11. They always give the vacant seats to _______ comes first. A. whoever B. whomever C. who D. whom 12. Doing your homework is a sure way to improve your test scores, and this is especially true _______ it comes to classroom tests. A. when B. since C. before D. after 13. Personal computers are no longer something beyond the ordinary people; they are _______ available these days. A. promptly B. instantly C. readily D. quickly 14. Owing to _______ competition among the airlines, travel expenses have been reduced considerably . A. fierce B. strained C. eager D. critical 15. Doctor often ______uneasiness in the people they deal with. A. smell B. sense C. hear D. tough Part II Word Match (15 points, 1 point each) Direction : Match the following words with their definitions within each group of five words. Write Group 1 1. authentic A. having powers of learning, reasoning or understanding 2. commitment B. twist; changing shape 3. exaggerate C. a promise or decision to do something 4. intelligent D. real; true and accurate 5. distortion E. say more than the truth about something Group 2 6. authority A. basic; central; forming the necessary basis of something 7. donate B. something that is considered more important than other matters 8. substantial C. the right or ability to control 9. priority D. give something for the benefit of others 10. fundamental E. large in size, value or importance Part III Sentence Completion (10 points, 1 point each) 1. George is not only a skillful painter, but also a ______ writer. (talent) 2. The ________ John to Mary was announced in the newspapers yesterday . (engage) 3. I love the movie because the _______ is my favorite. (act) 4. _______ to say , this absent-minded professor left his umbrella in the classroom again. (need) 5. I'm afraid the girl is a little ________ for her age and height. (weight)
毕业生就业演讲稿 各位老师，各位同学： 大家晚上好！ 大学生毕业找工作，是人生中一件非常重要的事情！ 一、作为即将毕业的大学生，应该敢于主动去找工作，敢于主动去寻找机会就业。 主动寻找就业，是职业生涯中一个非常关键的技巧，而不是等待家庭的安排或者是等待机会的到来；什么是就业？我的理解和新东方的总裁俞敏洪先生理解的几乎一样，就是找上一份工作，不管喜欢不喜欢，能有工作干，能通过自
己的努力得到一份薪水，不再需要花父母的钱，这就是就业。 二、工作都需要持之以恒、都需要认定工作是不分贵贱的。 一个人在工作岗位上，作为领导者，不是来看你今天跳槽明天跳槽的，他需要看见自己招聘的工作人员能安心守份地上班。 三、只有在寻找就业的时候放下自己，那么才能在工作中开心。 你可以让自己起点高，这是一个充分有自信的表现。但是能给你的岗位，也许并不是如你意的，或者还是与你专业背道相弛的，这个时候，要沉下心来，坚持你的岗位，坚持就业的方向。跳槽是允许的，但是一定要条件成熟。 初期的工作，一定要放下自己，调整好心态，这就是就业。 说了找工作，我们说说大学生应不应该一开始就创业。我的个人主张是，大学生不适合一走出校门就去创业，而
是要找了工作，得到锻炼并且有一定机会时候，再开始创业。当然，如果一直找不到工作，或者找了工作又无法忍受的时候，可以考虑创业，但是不要沉沦，一定要在任何时候，都要坚强地站起来。 我想告诉大家几点： 一、有知识，更应该适应社会环境的发展，使自己融入到社会大家庭中来；有知识，也要沉下心来，先找好工作，再展示能力，最后追求自己的理想； 二、不管是工作，还是自己创业，一定要建立在国家的稳定繁荣的基础上。我们要感谢我们稳定强大繁荣的祖国，给了我们这样的生存环境，我们更应该珍惜，更应该找好工作岗位，为国家的稳定繁荣做出自己的贡献！ 三、学会分享！不管是就业还是创业，与人分享，与人交往，是当代大学生适应社会的一种技能！所以，大家毕业后就赶快行动起来，为自己的就业去寻找机会吧！ 相信：天生我材必有用，千金
多危害公路桥梁设计标准 George C. Lee1 , Mai Tong2 and Phillip Yen3 摘要： 根据AASHTO标准LRFD在哲学的研究方法，一项具有比例的作为危险比较的标准被作为联邦公路管理局和土木工程硕士研究的课题。本文介绍的一般做法是由MCEER进行建立各种灾害事件及其影响，预计公路桥梁适当比较的平台。 1.0介绍： 除了正常的功能要求外，多重危害（如：如地震、风的风味,洪水、船舶碰撞,交通超载事故,和恐怖主义袭击等）必须适当考虑在公路桥梁设计内，。当前的AASHTO桥梁设计规范提供了每个载荷危害的详细危险识别。为进一步研究抗多种灾害的桥梁，有必要建立桥梁对接的测量标准。例如在返回期间或在某一时间内发生的概率超出标准的各种危害就可以用一个简单的标准来考虑解决。然而，它并不完全合理运用这种标准来校准，因为许多其他有影响的因素，如危害持续时间的不确定性，桥梁设计荷载的危险，关键部件的脆弱性，风险危害引起的后果，影响潜力的地区和损伤的桥梁可能会有所不同。事实上，在目前的AASHTO 标准规范，设计地震灾害定为475的回报期，其中已经有50年超出标准10%的历史。从NEHRP（NEHRP 2000）最近建议的基础上，还打算增加对重大桥梁的回报期至2000-2500年。正确的设计地震重现期仍在研究和专业的社会讨论。根据ASCE的07-95，风危害的回报期定于50年，根据FHWA HEC 18 冲刷的回报期定为100年。相比之下，根据设计的生命桥跨度（戈恩等2003），活负载的最高年限定为75年，目前尚没有统一的对跨板灾害发生频率的设计要求。 2.0AASHTO标准LRFD致多灾害大桥设计改进 美国公路桥梁设计的主旨是在于将标准规格的AASHTO标准过渡到AASHTO标准的LRFD上。在认识到LRFD设计方法的优势基础上，又因为设计上主要的不确定性来自需求装载危险。所以适当的对公路桥梁设计的多重危险的比较是非常重要的。 从AASHTO标准LRFD设计方法论的角度看，每一个桥梁的设计应为指定的极限状态。低强度的危害桥梁的经验，定期和极端灾害事件这两个的设计标准是极限状态的设计代表。这意味着，桥梁结构系统，包括其部分和连接的设计必须首先达到失效机制。因此，过度意外的构件要尽量避免，因为它可能会在对结构产生不利影响，不良的位置 导致损坏（如塑料合页）。 AASHTO标准LRFD不同于AASHTO是因为LRFD的设计不同于传统的ASD,.应力设计方法。建筑署设计的一个主要弱点是，没有考虑到既高于预期负荷概率和低于预期的实力在同一时间和地点发生，而把所有载荷和载荷组合一视同仁的看待。因此，它具有很少或根本没有设计标准之间的假设，以及许多实际性成分的桥梁，或实际发生的事件的概率（Kulicki 1999年）有直接关系。 为了克服ASD方法的不足，LRFD在标准偏差或者变异系数的随机变量- 破坏指数β（这是一个失败的概率测量给定的负载设置，该元件的标称电阻正在设计。）的规范基础上建立。 β值直接关系到失败的概率大小。依据以往对剪力和弯矩规格模拟和实际的桥梁的设计， 可靠性指标对其进行了评价模拟。可靠性指标的范围涵盖了从小于2广泛高于4。正如（诺瓦克1999）编制的数据表明，过去的做法是由β= 3.5表示，该值被选中作为对LRFD规范校准目标。β= 3.5对应的安全统一的概率（1 - 对失败的概率），这是等于或大于99.98％。 AASHTO标准LRFD的优点是，它提供了一个统一的概率为基础的标准来衡量一个桥梁设计的安全水平。最好是，如果有相类似的统一标准能为多种灾害对桥梁的影响进行比较，那么它将加强AASHTO标准LRFD，并提供一个危险因子校正负载坚实的基础。可惜的是，似乎没有一个可以给予灾害事件和上述原因很好的解释。继LRFD和比较缺乏统一的危害的标准在目前的多个危险桥梁设计视图的基本方法后，FHWA的研究任务是探索和建立一些可能的和合理的非均匀commeasurable标准。 3.0COMMEASURABLE准则的多种危害公路桥梁设计 单词“commeasurable”是指根据“平等”的基础上比较。从多种灾害影响或危害桥梁载荷校准比较方面说，“平等”是相当复杂的。例如，危害分类上，commeasurable回收期基础确定是建立对个人发生危害的基础上设计荷载的。在这方面，commeasurable 标准只考虑了灾害发生的不确定性; 而没有考虑造成危害的电阻结构。船只的大小和重量在特定河流的物理限制到导致了船舶碰撞是一种不能得到妥善的风险投资。因此，碰撞的影响不会随着时间显著变化。据测定，每一年的总碰撞事故与事故位置无关。 commeasurable标准的目标是不是要审判桥梁设计本身，而是提供一个“平等”的基础来评估桥梁上的一个潜在危险的事件可能造成的影响。上文指出了“平等”的基础，可以解释“发生”，“安全”，“维修费用”，“中断服务”等的不同之处。