اقتصاد خرد
| فارسی | English | |||||||||||||||||||||||||||||||||||||||
 اقتصاد خرد شاخهای از علم اقتصاد است که به مطالعه منحصر به فرد اقتصاد، تجزیه و تحلیل بازار، رفتار مصرف کنندگان و خانوارها و بنگاهها میپردازد و اساس آن مدلهای ریاضی است.اقتصاد خرد شاخهای از علم اقتصاد است که به چگونگی رفتار انسانها و انتخاب هایشان در سطح واحدهای خرد یا کوچک اقتصادی مانند یک فرد، یک بنگاه، یک صنعت یا بازار یک کالای خاص میپردازد و به چگونگی تعامل بین خریداران و مصرف کنندگان و عوامل موثر در انتخاب خریداران میپردازد به طور خاص اقتصاد خرد به الگوی عرضه و تقاضا برای کالاها و خدمات و همچنین تعیین قیمت خروجی در بازارهای خاص میپردازد و به طور معمول در بازار هایی که در آن کالاها در حال خرید و فروش هستند کاربرد دارد .
تفاوت بین اقتصاد خرد و کلان [ویرایش]علم اقتصاد به دو بخش اقتصاد خرد و اقتصاد کلان تقسیم میشود .اقتصاد کلان به مطالعه رفتار اقتصاد به عنوان یک صنعت کامل میپردازد و فقط در شرکتهای خاص مورد برسی قرار نمی دهد .این نگاه به پدیدههای اقتصادی گسترده ای مانند تولید ناخالص ملی، تورم، بیکاری، و سطوح قیمتها میپردازد . اقتصاد خرد نگاهی متمرکز در تئوریهای اساسی عرضه و تقاضا دارد این که چه مقدار از چیزی را برای تولید و چه مقدار را برای هزینه در نظر بگیریم را مورد بررسی قرار میدهد . در حالی که این دو شاخه اقتصاد به نظر میرسد از هم متفاوت باشند اما کاملا به هم وابسته و مکمل یکدیگرند و بسیاری از مسایل اقتصادی تداخلی از این دو مطالعه هستند .به عنوان مثال با افزایش نرخ تورم قیمت مواد اولیه افزایش می یابد و این به نوبهٔ خود در قیمت نهایی کالاها تاثیر گذار است . اهداف اقتصاد خرد [ویرایش]یکی از اهداف اقتصاد خرد بررسی بازار و برقرار کردن یک رابطهٔ نسبی پولی بین کالاها و خدمات است. همچنین به بررسی موارد شكست بازار (مواردي كه بازار قادر به تولید نتیجهٔ مطلوب و در خور نبوده اند) میپردازد. تئوری هایی را برای داشتن یک بازار رقابتی شرح میدهد. در نظریه عرضه و تقاضا معمولاً فرض بر این قرار داده میشود که فضا کاملا رقابتی است . این بدین معناست که خریداران و فروشندگان بسیاری در بازار وجود دارند و هیچ کدام از آنها نمی توانند بر قیمتها تاثیر بگذارند . درمعالات زندگی واقعی این فرض با مشکل مواجه است زیرا بسیاری از خریداران و فروشندگان این توانایی را دارند که بر قیمتها تاثیرگذار باشند . در خصوص نظریهٔ عرضه و تقاضا در اغلب موارد تجزیه و تحلیل پیچیده ای نیاز است تا بتوان یک مدل عرضه و تقاضا ارائه داد. زمینههای مهم در علم اقتصاد خرد [ویرایش]شامل برقراری تعادل عمومی، انتخاب تحت عدم اطمینان, تئوری بازیها و در نظر گرفتن کشش عرضه و تقاضا درون سیستم بازار است . منابع [ویرایش]ویکیپدیای انگلیسی http://en.wikipedia.org/wiki/Microeconomics Mas-Colell, Andreu, Michael D. Whinston & Jerry R. Green: Microeconomic Theory; دانشگاه آکسفورد Press. اقتصاد چیست؟، محمد مهدی بهکیش، نشر نی، چاپ دوم،۱۳۸۱ Rubinstein, Ariel: Lecture Notes in Microeconomic Theory; Princeton University Press طبیبیان، محمد: اقتصاد خرد پیشرفته (مباحثی از مبانی نظری و کاربرد آن)؛ انتشارات پیشبرد. جستارهای وابسته [ویرایش]
|
Microeconomics (from Greek prefix mikro- meaning "small" and economics) is a branch of economics that studies the behavior of individual households and firms in making decisions on the allocation of limited resources (see scarcity).[1] Typically, it applies to markets where goods or services are bought and sold. Microeconomics examines how these decisions and behaviors affect the supply and demand for goods and services, which determines prices, and how prices, in turn, determine the quantity supplied and quantity demanded of goods and services.[2][3] This is in contrast to macroeconomics, which involves the "sum total of economic activity, dealing with the issues of growth, inflation, and unemployment."[2] Microeconomics also deals with the effects of national economic policies (such as changing taxation levels) on the aforementioned aspects of the economy.[4] Particularly in the wake of the Lucas critique, much of modern macroeconomic theory has been built upon 'microfoundations'—i.e. based upon basic assumptions about micro-level behavior. One of the goals of microeconomics is to analyze market mechanisms that establish relative prices amongst goods and services and allocation of limited resources amongst many alternative uses. Microeconomics analyzes market failure, where markets fail to produce efficient results, and describes the theoretical conditions needed for perfect competition. Significant fields of study in microeconomics include general equilibrium, markets under asymmetric information, choice under uncertainty and economic applications of game theory. Also considered is the elasticity of products within the market system.
Assumptions and definitions [edit]
The theory of supply and demand usually assumes that markets are perfectly competitive. This implies that there are many buyers and sellers in the market and none of them have the capacity to significantly influence prices of goods and services. In many real-life transactions, the assumption fails because some individual buyers or sellers have the ability to influence prices. Quite often, a sophisticated analysis is required to understand the demand-supply equation of a good model. However, the theory works well in situations meeting these assumptions. Mainstream economics does not assume a priori that markets are preferable to other forms of social organization. In fact, much analysis is devoted to cases where so-called market failures lead to resource allocation that is suboptimal by some standard (defense spending is the classic example, profitable to all for use but not directly profitable for anyone to finance). In such cases, economists may attempt to find policies that will avoid waste, either directly by government control, indirectly by regulation that induces market participants to act in a manner consistent with optimal welfare, or by creating "missing markets" to enable efficient trading where none had previously existed. This is studied in the field of collective action and public choice theory. "Optimal welfare" usually takes on a Paretian norm, which in its mathematical application of Kaldor–Hicks method. This can diverge from the Utilitarian goal of maximizing utility because it does not consider the distribution of goods between people. Market failure in positive economics (microeconomics) is limited in implications without mixing the belief of the economist and their theory. The demand for various commodities by individuals is generally thought of as the outcome of a utility-maximizing process, with each individual trying to maximize their own utility under a budget constraint and a given consumption set. Modes of operation [edit]It is assumed that all firms are following rational decision-making, and will produce at the profit-maximizing output. Given this assumption, there are four categories in which a firm's profit may be considered to be.
Opportunity cost [edit]Main article: Opportunity cost
Opportunity cost of an activity (or goods) is equal to the best next alternative foregone. Although opportunity cost can be hard to quantify, the effect of opportunity cost is universal and very real on the individual level. In fact, this principle applies to all decisions, not just economic ones. Opportunity cost is one way to measure the cost of something. Rather than merely identifying and adding the costs of a project, one may also identify the next best alternative way to spend the same amount of money. The forgone profit of this next best alternative is the opportunity cost of the original choice. A common example is a farmer that chooses to farm their land rather than rent it to neighbors, wherein the opportunity cost is the forgone profit from renting. In this case, the farmer may expect to generate more profit alone. This kind of reasoning is a very important part of the calculation of discount rates in discounted cash flow investment valuation methodologies. Similarly, the opportunity cost of attending university is the lost wages a student could have earned in the workforce, rather than the cost of tuition, books, and other requisite items (whose sum makes up the total cost of attendance). Note that opportunity cost is not the sum of the available alternatives, but rather the benefit of the single, best alternative. Possible opportunity costs of a city's decision to build a hospital on its vacant land are the loss of the land for a sporting center, or the inability to use the land for a parking lot, or the money that could have been made from selling the land, or the loss of any of the various other possible uses — but not all of these in aggregate. The true opportunity cost would be the forgone profit of the most lucrative of those listed. One question that arises here is how to determine a money value for each alternative to facilitate comparison and assess opportunity cost, which may be more or less difficult depending on the things we are trying to compare. For example, many decisions involve environmental impacts whose monetary value is difficult to assess because of scientific uncertainty. Valuing a human life or the economic impact of an Arctic oil spill involves making subjective choices with ethical implications. It is imperative to understand that no decision on allocating time is free. No matter what one chooses to do, they are always giving something up in return. An example of opportunity cost is deciding between going to a concert and doing homework. If one decides to go the concert, then they are giving up valuable time to study, but if they choose to do homework then the cost is giving up the concert. Any decision in allocating capital is likewise: there is an opportunity cost of capital, or a hurdle rate, defined as the expected rate one could get by investing in similar projects on the open market. Opportunity cost is vital in understanding microeconomics and decisions that are made. Applied microeconomics [edit]
Applied microeconomics includes a range of specialized areas of study, many of which draw on methods from other fields. Industrial organization examines topics such as the entry and exit of firms, innovation, and the role of trademarks. Labor economics examines wages, employment, and labor market dynamics. Financial economics examines topics such as the structure of optimal portfolios, the rate of return to capital, econometric analysis of security returns, and corporate financial behavior. Public economics examines the design of government tax and expenditure policies and economic effects of these policies (e.g., social insurance programs). Political economy examines the role of political institutions in determining policy outcomes. Health economics examines the organization of health care systems, including the role of the health care workforce and health insurance programs. Urban economics, which examines the challenges faced by cities, such as sprawl, air and water pollution, traffic congestion, and poverty, draws on the fields of urban geography and sociology. Law and economics applies microeconomic principles to the selection and enforcement of competing legal regimes and their relative efficiencies. Economic history examines the evolution of the economy and economic institutions, using methods and techniques from the fields of economics, history, geography, sociology, psychology, and political science. Development [edit]Traditional Marginalism [edit]
The modern field of microeconomics arose as an effort of neoclassical economics school of thought to put economic ideas into mathematical mode. An early attempt was made by Antoine Augustine Cournot in Researches on the Mathematical Principles of the Theory of Wealth[5] (1838) in describing a spring water duopoly that now bears his name. Later, William Stanley Jevons's Theory of Political Economy[6] (1871), Carl Menger's Principles of Economics[7] (1871), and Léon Walras's Elements of Pure Economics: Or the theory of social wealth (1874–77)[8] gave way to what was called the Marginal Revolution. Some common ideas behind those works were models or arguments characterized by rational economic agents maximizing utility under a budget constrain. This arose as a necessity of arguing against the labour theory of value associated with classical economists such as Adam Smith, David Ricardo and Karl Marx. Walras also went as far as developing the concept of general equilibrium of an economy. Alfred Marshall's textbook, Principles of Economics[9] was published in 1890 and became the dominant textbook in England for a generation. His main point was that Jevons went too far in emphasizing utility as an attempt to explain prices over costs of production. In the book he writes:
In the same appendix[10] he further states:
Marshall's idea of solving the controversy was that the demand curve could be derived by aggregating individual consumer demand curves, which were themselves based on the consumer problem of maximizing utility. The supply curve could be derived by superimposing a representative firm supply curves for the factors of production and then market equilibrium would be given by the intersection of demand and supply curves. He also introduced the notion of different market periods: mainly short run and long run. This set of ideas gave way to what economists call perfect competition, now found in the standard microeconomics texts, even though Marshall himself had stated:[11]
An early formulation of the concept of production functions is due to Johann Heinrich von Thünen[12] which presented an exponential version of it. The standard Cobb–Douglas production function found in microeconomics textbooks refers to a collaborative paper between Charles Cobb and Paul Douglas published in 1928[13] in which they analised U.S. manufacturing data using this function as the basis of a regression analysis for estimating the relationship between inputs (labour and capital) and output (product): this discussion takes place through the concept of marginal productivity. The mathematical form of the Cobb-Douglas function can be found in the prior work of Knut Wicksell, Von Thunen and Turgot. An early procedure for constructing cost curves is presented by Jacob Viner is his “Cost Curves and Supply Curves” (1931)[14], the paper was an attempt to reconcile two streams of thought when dealing with this issue at the time: the idea that supplies of factors of production were given and independent of rate of remuneration (Austrian School) or dependent on rate of remuneration (English School, that is followers of Marshall). Viner argued that “the differences between the two schools would not affect qualitatively the character of the findings”, more specifically “that this concern is not of sufficient importance to bring about any change in the prices of the factors as a result of a change in its output”. He gives some definitions which are know that taken to be standard:
He explains that if the law of diminishing returns holds output per unit of variable factor will fall as total output rises, and that if the prices of the factors remain constant, then average direct costs will increase with output. Also if atomistic competition prevails, that is the individual firm output wont affect product prices, then the individual firm short-run supply curve equals the short run marginal cost curve. In the long run, the supply curve for industry can be constructed by summing individual marginal cost curves abscissas. He also explains that internal economies of scale are primarily a long-run phenomenon and are due either to reductions in the technical coefficients of production (technical economies=increasing productivity) or to discounts resulting from larger size (pecuniary economies). External economies of scale are also either technical or pecunary, but in this case are due to aggregate behavior of the industry. It should be made clear that these long-run results only hold if producer are rational actors, that is able to optimize their production so as to have an “optimal scale of plant”. Imperfect Competition and Game Theory [edit]A new impetus was given to field when around 1933. Joan Robinson and Edward H. Chamberlin, published respectively, The Economics of Imperfect Competition (1933) and The Theory of Monopolistic Competition (1933), introducing models of imperfect competition. Although the monopoly case was already exposed in Marshall's Principles of Economics and Cournot had already constructed models of duopoly and monopoly in 1838, a whole new set of models grew out of this new literature. In particular the monopolistic competition model results in a non efficient equilibrium. Chamberlin defined monopolistic competition as "challenge to traditional viewpoint of economics that competition and monopoly are alternatives and that individual prices are to be explained in terms of one or the other". He continues: "By contrast it is held that most economic situations are composite of both competition and monopoly, and that, wherever this is the case, a false view is given by neglecting either one of the two forces and regarding the situation as made up entirely of the other".[15] 
Later on some market models were built using game theory, particularly regarding oligopolies. A good example of how microeconomics started to incorporate game theory, is the Stackelberg competition model published in 1934[16] which can be characterized as a dynamic game with a leader and a follower, and then be solved to find a Nash Equilibrium. Externalities and Market Failure [edit]In 1937 The Nature of the Firm[17] was published by Ronald Coase introducing the notion of transaction costs (the term itself was coined in the fifties), which explained why firms have an advantage over a group of independent contractors working with each other. The idea was that there were transaction costs in the use of the market: search and information costs, bargaining costs, etc. which give an advantage to a firm which can internalize the production process required to deliver a certain good to the market. A related result was published by Coase in his “The Problem of Social Cost”[18] (1960) which analyses solutions of the problem of externalities through bargaining, in which he first describes a cattle herd invading a farmer's crop and then discusses four legal cases: Sturges v Bridgman, Cooke v Forbes, Bryant v Lejever and Bass v Gregory. He then states:
This then becomes relevant in context of regulations. He argues against the Pigovian tradition:[19]
This period also marks the beginning of mathematical modeling of public goods with Paul Samuelson's The Pure Theory of Public Expenditure (1954),[20] in it he gives a set of equations for efficient provision of public goods (he called them collective consumption goods), now know as the Samuelson condition. He then gives a description of what is know called the free rider problem:
Around the seventies the study of market failures came again into focus with the study of information asymmetry. In particular three authors emerged from this period: George Akerlof, Michael Spence and Joseph Stiglitz. Akerlof considered the problem of bad quality cars driving good quality cars out of the market in his know classic “The Market for Lemons”[21] (1970) because of the presence of asymmetrical information between buyers and sellers. Spence explained that signaling was fundamental in the labour market, because since employers can't know beforehand which of the candidates are the most productive, a college degree becomes a signaling device which allows a firm to hire new personnel.[22] A synthesizing paper of this era is "Externalities in Economies with Imperfect Information and Incomplete Markets" by Stiglitz and Greenwald:[23] the basic model consists of households maximizing a utility function, firms maximizing profit and a government which produces nothing, collect taxes and distribute the proceeds. An initial equilibrium with no taxes is assumed to exist, a vector x of household consumption and vector z of other variables that affect household utilities (externalities) are defined, a vector π of profits is defined along with a vector E of households expenditures. Since the envelope theorem holds, if the initial non taxed equilibrium is Pareto optimal then it follows that the dot products Π (between π and the time derivative of z) and B (between E and the time derivative of z) must equal each other. They state:
One application of this result is to the already mentioned Market for Lemons which deals with adverse selection: households buy from a pool of goods with heterogeneous quality considering only average quality, since in general the equilibrium is not efficient, any tax which raises average quality is beneficial (in the sense of optimal taxation). Other applications were considered by the authors, such as tax distortions, signaling, screening, moral hazard, incomplete markets, queue rationing, unemployment and rationing equilibrium. 
Behavioral Economics [edit]Kahneman and Tversky published their paper "Prospect Theory: An Analysis of Decision under Risk" in 1979 criticizing the very idea of the rational economic agent. The main point is that there an asymmetry in the psychology of the economic agent which gives a much higher value to losses than to gains. This article[24] is usually regarded as the beginning of behavioral economics and has consequences particularly regarding the world of finance. The authors summed the idea in the abstract as follows:
More recently, the continuing Great Recession brought the principal–agent problem again to the center of debate, in particular regarding corporate governance.[25] References [edit]
Further reading [edit]
External links [edit]
| |||||||||||||||||||||||||||||||||||||||
