Economic inequality refers to disparities in the distribution of economic assets and income. The term typically refers to inequality among individuals and groups within a society, but can also refer to inequality among nations. There is debate as to what equality should mean. Some think in terms of Equality of opportunity and others in terms of Equality of outcome.
There are many posited solutions from those who see economic inequality as improper; these solutions usually concentrate on equality of outcome and/or opportunity. Aside from the ethical arguments against inequality, there is evidence that " inequity aversion" is a shared human characteristic.
Economic inequality has always existed; its nature, cause and importance are open to broad debate. A country's economic structure or system (such as capitalism, socialism and everything in between), ongoing or past wars, and individuals' different abilities to create wealth are all involved in the creation of economic inequality.
Numerical indexes measuring economic inequality among individuals compares the well-being and numbers of the rich with those of the poor. Inequality is most often measured using the Gini coefficient (defined based on the Lorenz curve). For more details, see the article on income inequality metrics.
Economic inequality among different individuals or social groups is best measured within a single country. This is due to the fact that country-specific factors tend to obscure inter-country comparisons of individuals' incomes. A single nation will have more or less inequality depending on the social and economic structure of that country.
Causes of inequality
There are many reasons for economic inequality within societies. These causes are often inter-related and complex. For example, race differences and wealth condensation are different causes but can be highly correlated within a population. The relationship between cause and effect can also be non-linear and complex. For example, economic inequality decreases the amount of social cohesion within society, leading to greater inequality. Among the acknowledged factors that impact economic inequality in some part are the labour market, innate ability, education, race, gender, culture, wealth condensation, and development patterns.
The labour market
One of the major reasons there is economic inequality within modern market economies is because wages are determined by a market, and are hence influenced by supply and demand. In this view, inequality is caused by the differences in the supply and demand for different types of work.
A job where there are many willing workers (high supply) but only a small number of positions (low demand) will result in a low wage for that job. This is because competition between workers drives down the wage. An example of this would be low-skill jobs such as dish-washing or customer service. Because of the persistence of unemployment in market economies and the fact that these jobs require very little skill results in a very high supply of willing workers. Contrary wise, there is a limited number of jobs available. Competition amongst workers tend to drive down the wage since if any one worker demands a higher wage the employer can simply hire another employee at an equally low wage.
A job where there are few willing workers (low supply) but a large demand for the skills these workers have will results in high wages for that job. This is because competition between employers will drive up the wage. An example of this would be high-skill jobs such as engineers or capable CEOs. Competition amongst employers tend to drive up wages since if any one employer demands a low wage, the worker can simply quit and easily find a new job at a higher wage.
While the above examples tend to identify skill with high demand and wages, this is not necessarily the case. For example, highly skilled computer programmers in western countries have seen their wages suppressed by competition from equally skilled workers in India who are willing to accept a lower wage.
The final results amongst these supply and demand interactions is a gradation of different wages representing income inequality within society.
Many people believe that there is a connection between differences in innate ability, such as intelligence, strength, or charisma, and between an individuals level of wealth. Relating these innate abilities back to the labour market suggests that such innate abilities are in high demand relative to their supply and hence play a large role in increasing the wage of those who have them. Contrary wise, such innate abilities might also affect an individuals ability to operate within society in general, regardless of the labour market.
Various studies have been conducted on the correlation between IQ scores and wealth/income. The book titled " IQ and the Wealth of Nations", written by Dr. Richard Lynn, examines this relationship with limited success, while other peer-reviewed research papers have also come across harsh criticisms on their findings. Without further research on the topic, incorporating statistical models that are universally accepted, it is fairly difficult to come towards an objective conclusion on whether or not there is a relationship between intelligence and wealth/income.
One important factor in the creation of inequality is the variable ability of individuals to get an education. Education, especially education in an area where there is a high demand for workers, creates high wages for those with this education. Contrary wise, those who are unable to afford an education generally receive much lower wages. Many economists believe that a major reason the world has experienced increasing levels of inequality since the 1980s is because of an increase in the demand for highly skilled workers in high-tech industries. They believe that this has resulted in an increase in wages for those with an education, but has not increased the wages of those without an education, leading to greater inequality.
Gender, race, and culture
The existence of different genders, races and cultures within a society is also thought to contribute to economic inequality. The idea of the gender gap tries to explain the reasons there are different levels of income for different genders. Culture and religion are thought to play a role in creating inequality by either encouraging or discouraging wealth-acquiring behaviour and providing a basis for discrimination. It is felt that in many countries individuals belonging to certain racial and ethnic minorities are found more often among the poor than others. For those countries where this can be established, among the proposed causes for this discrepancy we find cultural differences amongst different races, an educational achievement gap, and racism.
Simon Kuznets argued that levels of economic inequality are in large part the result of stages of development. Kuznets saw a curve-like relationship between level of income and inequality. This relationship is now known as Kuznets curve. Supposedly, countries with low levels of development have relatively equal distributions of wealth. As a country develops, it acquires more capital, which leads to the owners of this capital having more wealth and income and introducing inequality. Eventually, through a variety of possible redistribution mechanisms such as trickle down effects and social welfare programs, more developed countries move back to lower levels of inequality. Kuznets showed this relationship as empirically strong using cross-sectional data. However, more recent testing of this theory with superior panel data has shown it to be very weak.
Wealth condensation is a theoretical process by which, in certain conditions, newly-created wealth tends to become concentrated in the possession of already-wealthy individuals or entities. This is reflected in the common saying 'the rich get richer and the poor get poorer' . According to this theory, those who already hold wealth have the means to invest in new sources of creating wealth or to otherwise leverage the accumulation of wealth, thus are the beneficiaries of the new wealth. Over time, wealth condensation can significantly contribute to the persistence inequality within society.
As an example of wealth condensation, truck drivers who own their own trucks consistently make more money than those who do not since the owner of a truck can escape the rent charged to drivers by owners (Even taking into account maintenance and other costs). Hence, a truck driver who has wealth to begin with can afford to buy his own truck in order to make more money. A truck driver who does not own his own truck makes a lesser wage and is therefore stuck in a Catch-22, unable to buy his own truck to increase his income.
Related to wealth condensation are the effects of inter generational inequality. It has been noted that the rich tend to provide their offspring with a better education, increasing their chances of achieving a high amount of income. Furthermore, the wealthy often leave their offspring with a hefty inheritance, jump starting the process of wealth condensation for the next generation.
There are many factors that tend to constrain the amount of economic inequality within society. Progressive taxation, where the rich are taxed more than poor, is effective at reducing the amount of income inequality in society. The Nationalization or subsidization of essential goods and services such as food, healthcare, education, and housing is also thought to reduce the amount of inequality in society. By providing goods and services that everyone needs for cheap or free, governments can effectively increase the disposable income of the poorer members of society.
Some have suggested that the rich do not value a dollar as much as the poor because of the decreasing marginal utility of wealth. They argue that this causes a redistribution of income towards the poor. This is popularly known as the " trickle down effect", and its effects are thought to be strongest in a booming "heated" economy.
It has also been suggested that any economic disparity will generate pressure for its own removal. Workers will be encouraged to unionize and will elect progressive politicians. This is often accomplished through the democratic system. However this can constrained by the ability of the wealthy to influence political power. Because of this, it is often thought that democracies tend to be more effective at countering inequality than dictatorships.
Effects of inequality
Research has shown a clear link between income inequality and social cohesion. In more equal societies, people are much more likely to trust each other, measures of social capital suggest greater community involvement, and homicide rates are consistently lower.
One of the earliest writers to note the link between economic equality and social cohesion was Alexis de Tocqueville in his Democracy in America. Writing in 1831:
- "Among the new objects that attracted my attention during my stay in the United States, none struck me with greater force than the equality of conditions. I easily perceived the enormous influence that this primary fact exercises on the workings of society. It gives a particular direction to the public mind, a particular turn to the laws, new maxims to those who govern, and particular habits to the governed... It creates opinions, gives rise to sentiments, inspires customs, and modifies everything it does not produce... I kept finding that fact before me again and again as a central point to which all of my observations were leading."
In 1997 Ichiro Kawachi and Bruce Kennedy showed that there is a high correlation between the amount of trust in society and the amount of income equality. They did this by comparing results from the question “would others take advantage of you if they got the chance?” in U.S General Social Survey with statistics on income inequality. Eric Uslander, in The Moral Foundations of Trust (2002), showed that a similar pattern exists through out the world.
Robert Putnam, professor of political science at Harvard, established links between social capital and economic inequality. His most important studies (Putnam, Leonardi, and Nanetti 1993, Putnam 2000) established these links in both the United States and in Italy. On the relationship of inequality and involvement in community he says:
- "Community and equality are mutually reinforcing… Social capital and economic inequality moved in tandem through most of the twentieth century. In terms of the distribution of wealth and income, America in the 1950s and 1960s was more egalitarian than it had been in more than a century… [T]hose same decades were also the high point of social connectedness and civic engagement. Record highs in equality and social capital coincided. Conversely, the last third of the twentieth century was a time of growing inequality and eroding social capital… The timing of the two trends is striking: somewhere around 1965-70 America reversed course and started becoming both less just economically and less well connected socially and politically." (Putnam 2000 pp 359)
If addition to effecting levels of trust and civic engagement, inequality in society has also shown to be highly correlated with crime rates. Most studies looking into the relationship between crime and inequality have concentrated on homocides - since homocides are almost identically defined across all nations and juristictions. There have been over fifty studies showing tendancies for violence to be more common in societies where income differnces are larger. Research has been conducted comparing developed countries with undeveloped countries, as well as studing areas within countries. Daly et al. 2001 found that among U.S States and Canadian Provinces there is a ten-fold difference in homicide rates related to inequality. They estimated that about half of all variations in homicide rates can be accounted for by differences in the amount of inequality in each province or state. Fajnzylber et al. 2002 found a similar relationship worldwide. Among comments in academic literature on the relationship between homicides and inequality are:
- "[T]he most consistent finding in cross-national research on homicides has been that of a positive association between income inequality and homicides."(Neapolitan 1999 pp 260)
- "[E]conomic inequality is positively and significantly related to rates of homicde despite an extensive list of conceptually relevant controls. The fact that this relationship is found with the most recent data and using a different measure of economic inequality from previous research, suggests that the finding is very robust." (Lee and Bankston 1999 pp 50)
Recently, there has been increasing interest from epidimiologists on the subject of economic inequality and its relation to the health of populations ( Population health). There is a very robust correlation between socioeconomic status and health. This correlation suggests that it is not only the poor who tend to be sick when everyone else is healthly, but that there is a continual gradient, from the top to the bottom of the socioeconomic ladder, relating status to health. This phenomenon is often called the " SES Gradient". Lower socioeconomic status has been linked to chronic stress, heart disease, ulcers, type 1 diabetes, rheumatoid arthritis, certain types of cancer, and premature aging.
Despite the reality of the SES Gradient, there is debate as to its cause. A number of researchers (A. Leigh, C. Jencks, A. Clarkwest - see also Russell Sage working papers) see a definite link between economic status and mortality due to the greater economic resources of the better-off, but they find little correlation due to social status differences.
Other researchers such as Richard Wilkinson, J. Lynch , and G.A. Kaplan have found that socioeconomic status strongly affects health even when controlling for economic resources and access to health care. Most famous for linking social status with health are the Whitehall studies - a series of studies conducted on civil servants in London. The studies found that, despite the fact that all civil servants in England have the same access to health care, there was a strong correlation between social status and health. The studies found that this relationship stayed strong even when controlling for health-effecting habits such as exercise, smoking and drinking. Furthermore, it has been noted that no amount of medical attention will help decrease the likelihood of someone getting type 1 diabetes or rheumatoid arthritis - yet both are more common among populations with lower socioeconomic status. Lastly, it has been found that amongst the wealthiest quarter of countries on earth (a set stretching from Luxembourg to Slovakia) there is no relation between a country's wealth and general population health - suggesting that past a certain level, absolute levels of wealth have little impact on population health, but relative levels within a country do.
The concept of psychosocial stress attempts to explain how psychosocial phenomenon such as status and social stratification can lead to the many diseases associated with the SES Gradient. Higher levels of economic inequality tend to intensify social hierarchies and generally degrades the quality of social relations - leading to greater levels of stress and stress related diseases. Richard Wilkinson found this to be true not only for the poorest members of society, but also for the wealthiest. Economic inequality is bad for everyone's health.
Inequality does not only affect the health of human populations. David H. Abbott at the Wisconsin National Primate Research Center found that among many primate species, less egalitarian social structures correlated with higher levels of stress hormones among socially subordinate individuals.
Economic inequality is thought to reduce distributive efficiency within society. That is to say, inequality reduces the sum total of personal utility because of the decreasing marginal utility of wealth. For example, a house may provide less utility to a single millionaire as a summer home than it would to a homeless family of five. The marginal utility of wealth is lowest among the richest. In other words, an additional dollar spent by a poor person will go to things providing a great deal of utility to that person, such as basic necessities like food, water, and healthcare; meanwhile, an additional dollar spent by a much richer person will most likely go to things providing relatively less utility to that person, such as luxury items. From this standpoint, for any given amount of wealth in society, a society with more equality will have higher aggregate utility. Some studies (Layard 2003;Blanchard and Oswald 2000, 2003) have found evidence for this theory, noting that in societies where inequality is lower, population wide satisfaction and happiness tend to be higher.
Many people accept inequality as a given, and argue that the prospect of greater material wealth provides incentives for competition and innovation within an economy.
Some modern economic theories, such as the neoclassical school, have suggested that a functioning economy requires a certain level of unemployment. These theories argue that unemployment benefits must be below the wage level to provide an incentive to work, thereby mandating inequality. Other theories, such as socialism, and Keynesianism dispute this alleged positive role of unemployment.
Several recent economists have investigated the relationship between inequality and economic growth. Robert Barro wrote a paper arguing that inequality reduces growth in poor countries and helps growth in rich ones. 
Many economists believe that one of the main reasons that inequality increases economic production is because material wellbeing and conspicuous consumption are related to status. In this view, high stratification of income (high inequality) creates high amounts of social stratification, leading to greater competition for status. One of the first writers to note this relationship was Adam Smith who recognized "regard" as one of the major driving forces behind economic activity. From The Theory of Moral Sentiments in 1759:
- "[W]hat is the end of avarice and ambition, of the pursuit of wealth, of power, and pre-eminence? Is it to supply the necessities of nature? The wages of the meanest labourer can supply them... [W]hy should those who have been educated in the higher ranks of life, regard it as worse than death, to be reduced to live, even without labour, upon the same simple fare with him, to dwell under the same lowly roof, and to be clothed in the same humble attire? From whence, then, arises that emulation which runs through all the different ranks of men, and what are the advantages which we propose by that great purpose of human life which we call bettering our condition? To be observed, to be attended to, to be taken notice of with sympathy, complacency, and approbation, are all the advantages which we can propose to derive from it. It is the vanity, not the ease, or the pleasure, which interests us."
-- Theory of Moral Sentiments, Part I, Section III, Chapter II
Modern sociologists and economists such as Juliet Schor and Robert H. Frank have studied the extent to which economic activity is fueled by the ability of consumption to represent social status. Schor, in The Overspent American, argues that the increasing inequality during the 1980s and 1990s strongly accounts for increasing aspirations of income, increased consumption, decreased savings, and increased debt. In Luxury Fever Robert H. Frank argues that people's satisfaction with their income is much more strongly affected by how it compares with others than its absolute level.
Views on inequality
In political philosophy, various schools of thought have different perspectives on inequality. Marxism favors an eventual communist society where distribution is based on an individual's needs rather than his ability to produce, social class, inheritance, or other such factors. In such a system inequality would be low or non-existent assuming everyone had the same "needs." Libertarianism generally does not take a stance on inequality per se, but opposes government intervention in society meaning that libertarians favor allowing inequality to remain as long as it is a result of the free market. Libertarian Robert Nozick argued that government redistributes wealth by force (usually in the form of taxation), and that the ideal, moral society would be one where all individuals are free from force. However, Nozick recognized that some modern economic inequalities were the result of forceful taking of property, and a certain amount of redistribution would be justified to compensate for this force but not because of the inequalities themselves. John Rawls argued in his A Theory of Justice that inequalities in the distribution of wealth are only justified when they improve society as a whole, including the least well off members. Rawls does not go into the full implications of his theory of justice. Some see Rawls's argument as a justification for capitalism since even the poorest members of society theoretically benefit from increased innovations under capitalism while others believe only a strong welfare state can statisfy Rawls's theory of justice.
In most western democracies, the desire to eliminate or reduce economic inequality is generally associated with the political left. The main practical argument in favor of reduction is the idea that economic inequality reduces social cohesion and increases social unrest, thereby weakening the society. There is evidence that this is true (see inequity aversion) and it is intuitively true, at least for small face-to-face groups of people. Related to this, Alberto Alesina, Rafael Di Tella, and Robert MacCulloch find that inequality negatively affects happiness in Europe but not in the United States. Also, there is the argument that economic inequality invariably translates to political inequality, which further aggravates the problem.
The acceptance of economic inequality is generally associated with the political right or at least that section of the right that is concerned with economics. The main practical argument in favor of the acceptance of economic inequality is that, as long as the cause is mainly due to differences in behaviour, the inequality serves as an economic engine to push the society towards economically healthy and efficient behaviour, and is therefore beneficial. This is intuitively true, at least for people who only interact economically. Also, it is pointed out that if one person earns $10 and the other earns $20, this is preferable to both earning $5, again, as long as the differential does not allow the person with $20 to buy enough influence to take away the other's earnings.
The main disagreement between the two sides is basically a disagreement on the importance of each effect, and the where the proper balance point should be. Both sides generally agree that the causes of economic inequality based on non-economic differences (race, gender, etc.) should be minimized. There is, of course, strong disagreement on how this minimization should be achieved.
Another point of view holds that "pure meritocracy is incoherent because, without redistribution, one generation's successful individuals would become the next generation's embedded caste, hoarding the wealth they had accumulated." (Patrick Diamond and Anthony Giddens, 27 June 2005, New Statesman) 
Critics Against Inequality as an Assessment for Economic Policy
Free market economists such as Milton Friedman argue that wealth is unlimited and growing and as such cannot be treated as a zero sum game: one person’s gain does not mean another necessarily loses. Furthermore, Friedman argues that capitalism, especially free market capitalism, results in voluntary transactions among parties and when transactions are voluntary no one is made worse off. Thus, when people act in a system of unlimited wealth and earn their wealth through voluntary transactions one person’s wealth rising faster than another is not a negative issue, and should not result in policies dedicated to wealth redistribution. Given these arguments, these microeconomists and free market thinkers believe that wealth redistribution is an irrational response and that economic inequality is neither unfair nor unjust.